We would like to thank Prof. Ferenc Krausz for the discussions and Najd Altwaijry for her support for finalizing the manuscript. This work has been financed by the Centre for Advanced Laser Applications (CALA).

<ol>
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The authors have nothing to disclose.

The turn-key operation of the oscillator is achieved by the optimum heat management of the different components of the laser. The output of the oscillator is reproducible on a daily basis, with no need for extra alignment or optimization. In addition, the pulse-to-pulse energy stability and spatial pointing stability of the seed laser fulfills the preconditions to achieving the stable operation of the regenerative amplifier.
Other low-energy seed sources, such as fiber amplifiers, can be used to seed the amplifier. In this study, a 2 &#181;J Yb:YAG thin-disk KLM oscillator was used to assist the amplification of the regenerative amplifier by reducing the growth of the accumulated nonlinear phases, since the required number of round trips is reduced for higher-input seed energy. Additionally, the higher seed energy influences the amplification process and reduces the gain narrowing. The measured spectral bandwidth of the amplified pulses for different seed energies at a fixed pump power is shown in Figure 5c. Amplified spectral bandwidth decreases for lower seed energies because of gain narrowing. For 10 pJ seed energy, the laser operates in the period doubling, and it is not possible to reach stable operation, even by increasing the number of round trips. In addition to the careful optimization of the cooling systems and the power supply of the diodes, the operation of the regenerative amplifier at saturation plays a major role in the achieved stability of the amplifier.
The fundamental or second harmonic of the laser can be used to pump an OPCPA system. For SHG, the performances of an LBO and a BBO crystal were compared, as they offer a high nonlinear coefficient and damage threshold, in spite of the larger spatial walk-off and the limited available aperture in the case of BBO. As the nonlinear coefficient of BBO is almost twice that of the LBO, a shorter crystal is sufficient to reach the saturation limit for SHG (Figure 6a). Therefore, BBO is the more suitable choice, as the accumulated nonlinear phase is smaller28.
The pulse durations of the SH pulses are characterized experimentally at different conversion efficiencies. It was observed that at high conversion efficiencies, the SHG spectrum is broadened and a higher-order spectral phase appears (Figure 6). Therefore, case B, with the conversion efficiency of 70%, is chosen where the SH and the unconverted fundamental beams maintain excellent quality.

The generation of high-energy, few-cycle laser pulses at a high repetition rate is of great interest to applied fields, such as attosecond science1,2,3,4 and high-field physics5,6, which stand to directly benefit from the availability of such sources. OPCPA represents the most promising route to achieving high pulse energies and large amplification bandwidths that simultaneously support few-cycle pulses1. To date, OPCPA allows for ultra-broadband amplification, which generates few-cycle pulses7,8,9,10. However, a modified implementation of the OPCPA scheme, which uses short pump pulses on the picosecond scale, holds promise for making this approach scalable for even higher pulse energies and average powers in the few-cycle regime1,11,12. Due to the high pump intensity in short-pulse pumped OPCPA, the high single-pass gain allows for the use of very thin crystals to support large amplification bandwidths. Although the short-pulse pumped OPCPA has many advantages, the realizability of this approach is subject to the availability of lasers that are specially tailored for this purpose. Such pump lasers are required to deliver high-energy picosecond pulses with near-diffraction limited beam quality at repetition rates in the kHz to MHz range13,14,15.
The introduction of ytterbium-doped lasers at different geometries, capable of delivering picosecond laser pulses with high energy and high average power, are about to change the current state of the field1,13,14,15,16,17,18. Yb:YAG has good thermal conductivity and a long upper-state lifetime, and it can be pumped by cost-effective diode lasers. Its performance when used in thin-disk geometry is outstanding due to the efficient cooling of the gain medium to simultaneously scale the peak and average power. Moreover, the occurrence of self-focusing inside the gain medium during the amplification process is suppressed due to the slenderness of the thin-disk in comparison to other gain medium geometries, resulting in excellent temporal and spatial profiles of the amplified pulses. Combining this concept with CPA holds promise for generating picosecond pulses with hundreds of millijoules of energy and hundreds of watts of average power19,20.
The aim of this work is to demonstrate a turn-key Yb:YAG thin-disk regenerative amplifier with outstanding daily performance as a suitable source for pumping OPCPAs21. To achieve this goal, this study employs a Yb:YAG thin-disk oscillator22 with several microjoules of pulse energy to seed the amplifier to minimize the accumulated nonlinear phase during the amplification process. This protocol provides the recipe for building and operating the laser system, which is described elsewhere21. Details about component implementation and control software are presented, and the alignment process of the system is described.

<table><tbody><tr><td>&lt;strong&gt;Electrooptics&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Fiber-Coupled Diode Laser Module</td><td>Dilas Diodenlaser GmbH</td><td>M1F8H12-940.5-500C-IS11.34</td><td></td></tr><tr><td>Fiber-Coupled Diode Laser Module</td><td>Laserline GmbH</td><td>LDM1000-500</td><td></td></tr><tr><td>Power Supply for Diode Laser</td><td>Delta Elektronika B.V.</td><td>SM 15-100</td><td></td></tr><tr><td>Power Supply for Diode Laser</td><td>Delta Elektronika B.V.</td><td>SM 35-45</td><td></td></tr><tr><td>Pulse Picker&#039;s Driver</td><td>Bergmann Messger&amp;auml;te Entwicklung KG&amp;nbsp;</td><td>N/A, customized</td><td></td></tr><tr><td>Pockels Cell&#039;s Driver</td><td>Bergmann Messger&amp;auml;te Entwicklung KG&amp;nbsp;</td><td>N/A, customized</td><td></td></tr><tr><td>Pulse Picker&#039;s Driver Power Supply</td><td>Bergmann Messger&amp;auml;te Entwicklung KG&amp;nbsp;</td><td>PCD8m7</td><td></td></tr><tr><td>Pockels Cell&#039;s Driver Power Supply</td><td>Bergmann Messger&amp;auml;te Entwicklung KG&amp;nbsp;</td><td>PCD8m7</td><td></td></tr><tr><td>Delay Generator PCI</td><td>Bergmann Messger&amp;auml;te Entwicklung KG&amp;nbsp;</td><td>BME_SG08p</td><td></td></tr><tr><td>Splitter Box</td><td>Bergmann Messger&amp;auml;te Entwicklung KG&amp;nbsp;</td><td>N/A, customized</td><td></td></tr><tr><td>Resonant Preamplifier</td><td>Bergmann Messger&amp;auml;te Entwicklung KG&amp;nbsp;</td><td>BME_P03</td><td></td></tr><tr><td>Pulse Picker&#039;s crystal</td><td>Castech Inc.</td><td>N/A, customized</td><td>12*12*20 mm&amp;sup3;</td></tr><tr><td>Pockels Cell&#039;s crystal</td><td>Castech Inc.</td><td>N/A, customized</td><td>12*12*20 mm&amp;sup3;</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Optics&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Thin-disk</td><td>TRUMPF Scientific Lasers&amp;nbsp;</td><td>N/A, customized</td><td></td></tr><tr><td>Thin-disk Head</td><td>TRUMPF Scientific Lasers&amp;nbsp;</td><td>N/A, customized</td><td></td></tr><tr><td>Fiber</td><td>Frank Optic Products GmbH</td><td>N/A, customized</td><td></td></tr><tr><td>Fiber Objective</td><td>Edmund Optics GmbH</td><td>N/A, customized</td><td></td></tr><tr><td>Faraday Isolator</td><td>Electro-Optics Technology, Inc</td><td>EOT.189.12231</td><td></td></tr><tr><td>Faraday Rotator</td><td>Electro-Optics Technology, Inc</td><td>EOT.189.22040</td><td></td></tr><tr><td>Stretcher&#039;s Grating 1</td><td>Horiba Jobin Yvon GmbH</td><td>N/A, customized</td><td>60*40*10 mm&amp;sup3;</td></tr><tr><td>Stretcher&#039;s Grating 2</td><td>Horiba Jobin Yvon GmbH</td><td>N/A, customized</td><td>350*190*50 mm&amp;sup3;</td></tr><tr><td>Compressor&#039;s Grating 1</td><td>Plymouth Grating Laboratory, Inc.</td><td>N/A, customized</td><td>40*40*16 mm&amp;sup3;</td></tr><tr><td>Compressor&#039;s Grating 2</td><td>Plymouth Grating Laboratory, Inc.</td><td>N/A, customized</td><td>300*100*50 mm&amp;sup3;</td></tr><tr><td>HR Mirror, 1&quot; (1030nm), flat, 0&amp;deg;</td><td>Layertec GmbH</td><td>108060</td><td></td></tr><tr><td>HR Mirror, 1&quot; (1030nm), flat, 0&amp;deg;</td><td>Laseroptik GmbH</td><td>B-09965, S-04484</td><td></td></tr><tr><td>HR Mirror, 1&quot; (1030nm), flat, 45&amp;deg;</td><td>Layertec GmbH</td><td>108063</td><td></td></tr><tr><td>HR Mirror, 1&quot; (1030nm), flat, 45&amp;deg;</td><td>Laseroptik GmbH</td><td>B-09966, S-04484</td><td></td></tr><tr><td>HR Mirror, 1&quot; (1030nm), curved</td><td>Layertec GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>HR Mirror, 2&quot; (1030nm), flat, 0&amp;deg;</td><td>Laseroptik GmbH</td><td>B-09965, S-05474</td><td></td></tr><tr><td>HR Mirror, 2&quot; (1030nm), flat, 45&amp;deg;</td><td>Laseroptik GmbH</td><td>B-09966, S-05474</td><td></td></tr><tr><td>Thin Film Polarizer (1030nm), 2&quot;</td><td>Layertec GmbH</td><td>103930</td><td></td></tr><tr><td>Waveplate L/2 (1030nm)</td><td>Layertec GmbH</td><td>106058</td><td>&amp;Oslash;=25mm</td></tr><tr><td>Waveplate L/4 (1030nm)</td><td>Layertec GmbH</td><td>106060</td><td>&amp;Oslash;=25mm</td></tr><tr><td>AR Window (1030nm), wedge</td><td>Laseroptik GmbH</td><td>B-00183-01, S-00988</td><td>&amp;Oslash;=38mm</td></tr><tr><td>Output Coupler, 1&quot; (1030nm)</td><td>Layertec GmbH</td><td>N/A, customized</td><td>PR = 88 %</td></tr><tr><td>High-dispersion Mirror (1030nm)</td><td>UltraFast Innovations GmbH</td><td>N/A, customized</td><td>GDD = -3000 fs&amp;sup2;</td></tr><tr><td>Lens, 1&quot; (1030nm), Plano-Convex</td><td>Thorlabs GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>Lens, 1&quot; (1030nm), Plano-Concave</td><td>Thorlabs GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>Lens, 2&quot; (1030nm), Plano-Convex</td><td>Thorlabs GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>Lens, 2&quot; (1030nm), Plano-Concave</td><td>Thorlabs GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>HR Mirror, 1&quot; (515nm), flat, 0&amp;deg;</td><td>Layertec GmbH</td><td>129784</td><td></td></tr><tr><td>HR Mirror, 1&quot; (515nm), flat, 0&amp;deg;</td><td>Eksma Optics</td><td>042-0515-i0</td><td></td></tr><tr><td>HR Mirror, 1&quot; (515nm), flat, 45&amp;deg;</td><td>Layertec GmbH</td><td>110924</td><td></td></tr><tr><td>HR Mirror, 1&quot; (515nm), flat, 45&amp;deg;</td><td>Eksma Optics</td><td>042-0515</td><td></td></tr><tr><td>HR Mirror, 1&quot; (515nm), curved</td><td>Layertec GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>HR Mirror, 1&quot; (515nm), curved</td><td>Eksma Optics</td><td>N/A, customized</td><td>set</td></tr><tr><td>HR Mirror, 2&quot; (515nm), flat, 0&amp;deg;</td><td>Eksma Optics</td><td>045-0515-i0</td><td></td></tr><tr><td>HR Mirror, 2&quot; (515nm), flat, 45&amp;deg;</td><td>Eksma Optics</td><td>045-0515</td><td></td></tr><tr><td>Thin Film Polarizer (515nm), 2&quot;</td><td>Layertec GmbH</td><td>112544</td><td></td></tr><tr><td>Waveplate L/2 (515nm)</td><td>Layertec GmbH</td><td>112546</td><td>&amp;Oslash;=25mm</td></tr><tr><td>Lens, 1&quot; (515nm), Plano-Convex</td><td>Thorlabs GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>Lens, 1&quot; (515nm), Plano-Concave</td><td>Thorlabs GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>Kerr Medium</td><td>Meller Optics, Inc.</td><td>N/A, customized</td><td>Sapphire, 1mm</td></tr><tr><td>BBO Crystal</td><td>Castech Inc.</td><td>N/A, customized</td><td>7*7*1.5 mm&amp;sup3;</td></tr><tr><td>Harmonic Separator, 1&quot;, 45&amp;deg;</td><td>Eksma Optics</td><td>042-5135</td><td></td></tr><tr><td>Harmonic Separator, 2&quot;, 45&amp;deg;</td><td>Eksma Optics</td><td>045-5135</td><td></td></tr><tr><td>Silver Mirror, 1&quot;, flat</td><td>Thorlabs GmbH</td><td>PF10-03-P01</td><td></td></tr><tr><td>Silver Mirror, 1&quot;, curved</td><td>Eksma Optics</td><td>N/A, customized</td><td>set</td></tr><tr><td>Filter - Absorptive Neutral Density</td><td>Thorlabs GmbH</td><td>NE##A</td><td>set</td></tr><tr><td>Filter - Reflective Neutral Density</td><td>Thorlabs GmbH</td><td>ND##A</td><td>set</td></tr><tr><td>Filter - Round Continuously Variable</td><td>Thorlabs GmbH</td><td>NDC-50C-4M</td><td></td></tr><tr><td>Filter - Edgepass Filter (Longpass)</td><td>Thorlabs GmbH</td><td>FEL####</td><td>set</td></tr><tr><td>Filter - Edgepass Filter (Shortpass)</td><td>Thorlabs GmbH</td><td>FES####</td><td>set</td></tr><tr><td>Wedge</td><td>Thorlabs GmbH</td><td>N/A, customized</td><td>set</td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Optomechanics &amp;amp; Motion&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Mirror Mount 1&quot; (small)</td><td>S. Maier GmbH</td><td>S1M4-##-1&amp;rdquo;</td><td></td></tr><tr><td>Mirror Mount 1&quot; (large)</td><td>S. Maier GmbH</td><td>S3-##</td><td></td></tr><tr><td>Mirror Mount 1&quot;</td><td>TRUMPF Scientific Lasers&amp;nbsp;</td><td>1&quot; adjustable&amp;nbsp;</td><td></td></tr><tr><td>Mirror Mount 2&quot;</td><td>S. Maier GmbH</td><td>S4-##</td><td></td></tr><tr><td>Mirror Mount 2&quot;</td><td>TRUMPF Scientific Lasers&amp;nbsp;</td><td>2&quot; adjustable&amp;nbsp;</td><td></td></tr><tr><td>Rotation Mount 1&amp;rdquo;</td><td>S. Maier GmbH</td><td>D25</td><td></td></tr><tr><td>Rotation Mount 1&amp;rdquo;</td><td>Thorlabs GmbH</td><td>RSP1/M</td><td></td></tr><tr><td>Rotation Mount 2&amp;rdquo;</td><td>Thorlabs GmbH</td><td>RSP2/M</td><td></td></tr><tr><td>Precision Rotation Stage</td><td>Newport Corporation</td><td>M-UTR120</td><td></td></tr><tr><td>Four-Axis Diffraction Grating Mount</td><td>Newport Corporation</td><td>DGM-1</td><td></td></tr><tr><td>Translation Stage</td><td>OptoSigma Corporation</td><td>TADC-651SR25-M6</td><td></td></tr><tr><td>Pockels cell stage</td><td>Newport Corporation</td><td>9082-M</td><td></td></tr><tr><td>Pockels Cell Holder</td><td>Home-made</td><td>N/A, customized</td><td></td></tr><tr><td>Picomotor Controller/Driver Kit</td><td>Newport Corporation</td><td>8742-12-KIT</td><td></td></tr><tr><td>Picomotor Piezo Linear Actuators</td><td>Newport Corporation</td><td>8301NF</td><td></td></tr><tr><td>Picomotor Rotation Mount</td><td>Newport Corporation</td><td>8401-M</td><td></td></tr><tr><td>Hand Control Pad</td><td>Newport Corporation</td><td>8758</td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Light Analysis&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Beam Profiling Camera</td><td>Ophir Optronics Solutions Ltd</td><td>SP620</td><td></td></tr><tr><td>Beam Profiling Camera</td><td>DataRay Inc.</td><td>WCD-UCD23</td><td></td></tr><tr><td>Photodiodes (solw)</td><td>Thorlabs GmbH</td><td>DET10A/M</td><td></td></tr><tr><td>Photodiodes (fast)</td><td>Alphalas GmbH</td><td>UPD-200-SP</td><td></td></tr><tr><td>Thin-disk Camera</td><td>Imaging Development Systems GmbH</td><td>UI-2220SE-M-GL</td><td></td></tr><tr><td>Oscilloscope</td><td>Tektronix GmbH</td><td>DPO5204</td><td></td></tr><tr><td>Oscilloscope</td><td>Teledyne LeCroy GmbH</td><td>SDA 760Zi-A</td><td></td></tr><tr><td>Spectrometer</td><td>Avantes</td><td>AvaSpec-ULS3648-USB2</td><td></td></tr><tr><td>Spectrometer</td><td>Ocean Optics, Inc</td><td>HR4C1769</td><td></td></tr><tr><td>Spectrometer</td><td>Ocean Optics, Inc</td><td>HR4C3762</td><td></td></tr><tr><td>Spectrometer</td><td>Ocean Optics, Inc</td><td>HR4D464</td><td></td></tr><tr><td>Spectrometer</td><td>Ocean Optics, Inc</td><td>HR4D466</td><td></td></tr><tr><td>Laser Thermal Power Sensor</td><td>Ophir Optronics Solutions Ltd</td><td>L50(150)A-PF-35</td><td></td></tr><tr><td>Laser Thermal Power Sensor</td><td>Ophir Optronics Solutions Ltd</td><td>FL500A</td><td></td></tr><tr><td>Laser Thermal Power Sensor</td><td>Ophir Optronics Solutions Ltd</td><td>3A-P-V1</td><td></td></tr><tr><td>Power and Energy Meter</td><td>Ophir Optronics Solutions Ltd</td><td>Vega</td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Systems&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Laser Beam Stabilization System</td><td>TEM-Messtechnik GmbH</td><td>Aligna</td><td></td></tr><tr><td>Laser M&amp;sup2; Measuring System</td><td>Ophir Optronics Solutions Ltd</td><td>M&amp;sup2;-200s</td><td></td></tr><tr><td>FROG</td><td>Home-made</td><td>N/A, customized</td><td></td></tr><tr><td>XFROG</td><td>Home-made</td><td>N/A, customized</td><td></td></tr><tr><td>&lt;strong&gt;Name&lt;/strong&gt;</td><td>&lt;strong&gt;Company&lt;/strong&gt;</td><td>&lt;strong&gt;Catalog Number&lt;/strong&gt;</td><td>&lt;strong&gt;Comments&lt;/strong&gt;</td></tr><tr><td>&lt;strong&gt;Miscellaneous&lt;/strong&gt;</td><td></td><td></td><td></td></tr><tr><td>Cooling Chiller</td><td>H.I.B Systemtechnik GmbH</td><td>6HE-000800-W-W-R23-2-DI</td><td></td></tr><tr><td>Cooling Chiller</td><td>Termotek GmbH</td><td>P201</td><td></td></tr><tr><td>Cooling Chiller</td><td>Termotek GmbH</td><td>P208</td><td></td></tr><tr><td>Laser Safety Goggles</td><td>Protect - Laserschutz GmbH</td><td>BGU 10-0165-G-20</td><td></td></tr><tr><td>Infra-red Viewer</td><td>FJW Optical Systems</td><td>84499A</td><td></td></tr><tr><td>Laser Viewing Card</td><td>Thorlabs GmbH</td><td>VRC4</td><td></td></tr><tr><td>Laser Viewing Card</td><td>Thorlabs GmbH</td><td>VRC5</td><td></td></tr><tr><td>Laser Viewing Card</td><td>Laser Components GmbH</td><td>LDT-1064 BG</td><td></td></tr><tr><td>Flowmeter</td><td>KOBOLD Messring GmbH</td><td>DTK-1250G2C34P</td><td></td></tr><tr><td>Pressure Gauge</td><td>KOBOLD Messring GmbH</td><td>EN 837-1</td><td></td></tr><tr><td>Temperature Sensor</td><td>KOBOLD Messring GmbH</td><td>TDA-15H* ***P3M</td><td></td></tr><tr><td>WinLase Software</td><td>Dr. C. Horvath &amp;amp; Dr. F. Loesel</td><td>WinLase Version 2.1 pro.</td><td>Laser Cavity Software</td></tr></tbody></table>

20 mj, 1 ps yb:yag thin-disk regenerative amplifier

This is a report on a 100 W, 20 mJ, 1 ps Yb:YAG thin-disk regenerative amplifier. A homemade Yb:YAG thin-disk, Kerr-lens mode-locked oscillator with turn-key performance and microjoule-level pulse energy is used to seed the regenerative chirped-pulse amplifier. The amplifier is placed in airtight housing. It operates at room temperature and exhibits stable operation at a 5 kHz repetition rate, with a pulse-to-pulse stability less than 1%. By employing a 1.5 mm-thick beta barium borate crystal, the frequency of the laser output is doubled to 515 nm, with an average power of 70 W, which corresponds to an optical-to-optical efficiency of 70%. This superior performance makes the system an attractive pump source for optical parametric chirped-pulse amplifiers in the near-infrared and mid-infrared spectral range. Combining the turn-key performance and the superior stability of the regenerative amplifier, the system facilitates the generation of a broadband, CEP-stable seed. Providing the seed and pump of the optical parametric chirped-pulse amplification (OPCPA) from one laser source eliminates the demand of active temporal synchronization between these pulses. This work presents a detailed guide to set up and operate a Yb:YAG thin-disk regenerative amplifier, based on chirped-pulse amplification (CPA), as a pump source for an optical parametric chirped-pulse amplifier.

The oscillator delivers 350 fs, 2 &#181;J, 25-W pulses at 11 MHz repetition rate, with a pulse-to-pulse stability of 1% (rms) and beam-pointing fluctuations of less than 0.6% over 1 h of measurement (Figure 4).
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/55717/55717fig4.jpg" /> 
Figure 4: Yb:YAG thin-disk, Kerr-lens mode-locked oscillator. (a) The spectrum (red), the retrieved temporal intensity profile (blue), and the spatial profile (inset) of the oscillator pulses. (b) Measured and retrieved SHG-FROG spectrograph of the oscillator. This figure has been modified from Fattahi et al., with permission from reference21. <a href="http://cloudflare.jove.com/files/ftp_upload/55717/55717fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The seed pulses are amplified in the regenerative amplifier to 125 W while being pumped with a CW fiber-coupled diode at a wavelength of 940 nm at 280 W, corresponding to an optical-to optical efficiency of 47%. The pulse-to-pulse stability of the amplifier is less than 1%, and the amplifier exhibits excellent long-term stability after 10 h of continuous operation. The amplified beam has an excellent spatial profile, with a M2 of 1 (M2x = 1.08 and M2y = 1.07) and an excellent temporal profile after compression to 1 ps (at FWHM) (Figure 5).
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/55717/55717fig5.jpg" /> 
Figure 5: Characterization of the regenerative amplifier output and the gain-narrowing effect. (a) The stability of the regenerative amplifier average power after 10 h of continuous operation. Inset: (a-1) Normalized power to its mean value in a time window of 0.5 h; (a-2) Output beam profile of the regenerative amplifier. (b) Amplifier output spectrum (green) and the retrieved temporal intensity (blue) of the laser pulses at 100 W average power after the grating compressor. (c) Seed energy versus spectral bandwidth (FWHM) of the amplifier output and the required round trips for the same output average power at 300 W of pump power. This figure has been modified from Fattahi et al., with permission from reference21. <a href="http://cloudflare.jove.com/files/ftp_upload/55717/55717fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
The SHG was analyzed using the SISYFOS code25. Two different crystals with the following parameters were considered: 1) a type-I, 6 mm-thick lithium triborate (LBO), with a phase-matching angle of 13.7&#176; and a nonlinear coefficient of 0.819 pm/V, and 2) a type-I, 3 mm-thick BBO with a phase-matching angle of 23.4&#176; and a nonlinear coefficient of 2 pm/V26,27. 1-ps, 20-mJ pulses at 1,030 nm and a peak intensity of 100 GW/cm2 were considered as the input of the simulation. The simulation results showed that the BBO performance was superior to that of the LBO for SHG (Figure 6).
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/55717/55717fig6.jpg" /> 
Figure 6: Second harmonic generation. (a) Simulated SHG energy for a 6 mm-thick LBO crystal and a 3 mm-thick BBO crystal. (b) Experimental SHG efficiency versus input pump peak intensity in a 1.5 mm-thick BBO crystal using 0.5 mJ (black) and 20 mJ (green) of the amplifier output. (c) The retrieved spectral intensity and (d) the group delay of XFROG measurements for different SHG efficiencies corresponding to points A, B, and C in (b). This figure has been modified from Fattahi et al., with permission from reference21. <a href="http://cloudflare.jove.com/files/ftp_upload/55717/55717fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>

Watch this Scientific Journal Video about 20 mJ, 1 ps Yb:YAG Thin-disk Regenerative Amplifier at JoVE.com

20 mJ, 1 ps Yb:YAG Thin-disk Regenerative Amplifier

A protocol for the operation of a high-energy, high-power optical parametric chirped pulse amplifier pump source based on an Yb:YAG thin-disk regenerative amplifier is presented here.

This is a report on a 100 W, 20 mJ, 1 ps Yb:YAG thin-disk regenerative amplifier. A homemade Yb:YAG thin-disk, Kerr-lens mode-locked oscillator with ...

20-mj-1-ps-ybyag-thin-disk-regenerative-amplifier

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11.4K Views.  Ludwig Maximilian University of Munich. A protocol for the operation of a high-energy, high-power optical parametric chirped pulse amplifier pump source based on an Yb:YAG thin-disk regenerative amplifier is presented here.

Video: 20 mJ, 1 ps Yb:YAG Thin-disk Regenerative Amplifier

Hyperpolarized Xenon for NMR and MRI Applications

Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 T generate only a small detectable net-magnetization of the sample at room temperature 1. Hence, most NMR and MRI applications rely on the detection of molecules at relative high concentration (e.g., water for imaging of biological tissue) or require excessive acquisition times. This limits our ability to exploit the very useful molecular specificity of NMR signals for many biochemical and medical applications. However, novel approaches have emerged in the past few years: Manipulation of the detected spin species prior to detection inside the NMR/MRI magnet can dramatically increase the magnetization and therefore allows detection of molecules at much lower concentration 2.
Here, we present a method for polarization of a xenon gas mixture (2-5% Xe, 10% N2, He balance) in a compact setup with a ca. 16000-fold signal enhancement. Modern line-narrowed diode lasers allow efficient polarization 7 and immediate use of gas mixture even if the noble gas is not separated from the other components. The SEOP apparatus is explained and determination of the achieved spin polarization is demonstrated for performance control of the method.
The hyperpolarized gas can be used for void space imaging, including gas flow imaging or diffusion studies at the interfaces with other materials 8,9. Moreover, the Xe NMR signal is extremely sensitive to its molecular environment 6. This enables the option to use it as an NMR/MRI contrast agent when dissolved in aqueous solution with functionalized molecular hosts that temporarily trap the gas 10,11. Direct detection and high-sensitivity indirect detection of such constructs is demonstrated in both spectroscopic and imaging mode.

The production of hyperpolarized xenon by means of spin exchange optical pumping (SEOP) is described. This method yields a ~10000-fold enhancement of the nuclear spin polarization of Xe-129 and has applications in nuclear magnetic resonance spectroscopy and imaging. Examples of gas phase and solution state experiments are given.

Nuclear magnetic resonance (NMR) spectroscopy and imaging (MRI) suffer from intrinsic low sensitivity because even strong external magnetic fields of ~10 ...

Engineering

Gradient Echo Quantum Memory in Warm Atomic Vapor

Gradient echo memory (GEM) is a protocol for storing optical quantum states of light in atomic ensembles. The primary motivation for such a technology is that quantum key distribution (QKD), which uses Heisenberg uncertainty to guarantee security of cryptographic keys, is limited in transmission distance. The development of a quantum repeater is a possible path to extend QKD range, but a repeater will need a quantum memory. In our experiments we use a gas of rubidium 87 vapor that is contained in a warm gas cell. This makes the scheme particularly simple. It is also a highly versatile scheme that enables in-memory refinement of the stored state, such as frequency shifting and bandwidth manipulation. The basis of the GEM protocol is to absorb the light into an ensemble of atoms that has been prepared in a magnetic field gradient. The reversal of this gradient leads to rephasing of the atomic polarization and thus recall of the stored optical state. We will outline how we prepare the atoms and this gradient and also describe some of the pitfalls that need to be avoided, in particular four-wave mixing, which can give rise to optical gain.

The gradient echo memory is a protocol for storing optical quantum states of light in atomic ensembles. Quantum memory is a key element of a quantum repeater, which can extend the range of quantum key distribution. We outline the operation of the scheme when implemented in a 3-level atomic ensemble.

Gradient  echo memory (GEM) is a protocol for storing optical quantum states of light in  atomic ensembles. The primary motivation for such a technology ...

Construction and Characterization of External Cavity Diode Lasers for Atomic Physics

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and Titanium Sapphire lasers as the workhorse laser of atomic physics labs1,2. Their versatility and prolific use throughout atomic physics in applications such as absorption spectroscopy and laser cooling1,2 makes it imperative for incoming students to gain a firm practical understanding of these lasers. This publication builds upon the seminal work by Wieman3, updating components, and providing a video tutorial. The setup, frequency locking and performance characterization of an ECDL will be described. Discussion of component selection and proper mounting of both diodes and gratings, the factors affecting mode selection within the cavity, proper alignment for optimal external feedback, optics setup for coarse and fine frequency sensitive measurements, a brief overview of laser locking techniques, and laser linewidth measurements are included.

This is an instructional paper to guide the construction and diagnostics of external cavity diode lasers (ECDLs), including component selection and optical alignment, as well as the basics of frequency reference spectroscopy and laser linewidth measurements for applications in the field of atomic physics.

Since their development in the late 1980s, cheap, reliable external cavity diode lasers (ECDLs) have replaced complex and expensive traditional dye and ...

Stimulated Stokes and Antistokes Raman Scattering in Microspherical Whispering Gallery Mode Resonators

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres can be thought as a store of energy with a huge variety of applications: compact laser sources, highly sensitive biochemical sensors and nonlinear phenomena. A protocol for the fabrication of both the microspheres and coupling system is given. The couplers described here are tapered fibers. Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility &#935;(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS). A proof of the cavity-enhanced phenomenon is given by the lack of correlation among the pump, signal and idler: a resonant mode has to exist in order to obtain the pair of signal and idler. In the case of hyperparametric oscillations (four wave mixing and stimulated anti-stokes Raman scattering), the modes must fulfill the energy and momentum conservation and, last but not least, have a good spatial overlap.

Efficient generation of nonlinear phenomena related to third order optical non-linear susceptibility &#935;(3) interactions in triply resonant silica microspheres is presented in this paper. The interactions here reported are: Stimulated Raman Scattering (SRS), and four wave mixing processes comprising Stimulated Anti-stokes Raman Scattering (SARS).

Dielectric microspheres can confine light and sound for a length of time through high quality factor whispering gallery modes (WGM). Glass microspheres ...

Cooling an Optically Trapped Ultracold Fermi Gas by Periodical Driving

We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs the anharmonicity of the ODT, in which the hotter atoms at the edge of the trap feel the anharmonic components of the trapping potential, while the colder atoms in the center of the trap feel the harmonic one. By modulating the trap depth with frequencies that are resonant with the anharmonic components, we selectively excite the hotter atoms out of the trap while keeping the colder atoms in the trap, generating parametric cooling. This experimental protocol starts with a magneto-optical trap (MOT) that is loaded by a Zeeman slower. The precooled atoms in the MOT are then transferred to an ODT, and a bias magnetic field is applied to create an interacting Fermi gas. We then lower the trapping potential to prepare a cold Fermi gas near the degenerate temperature. After that, we sweep the magnetic field to the noninteracting regime of the Fermi gas, in which the parametric cooling can be manifested by modulating the intensity of the optical trapping beams. We find that the parametric cooling effect strongly depends on the modulation frequencies and amplitudes. With the optimized frequency and amplitude, we measure the dependence of the cloud energy on the modulation time. We observe that the cloud energy is changed in an anisotropic way, where the energy of the axial direction is significantly reduced by parametric driving. The cooling effect is limited to the axial direction because the dominant anharmonicity of the crossed-beam ODT is along the axial direction. Finally, we propose to extend this protocol for the trapping potentials of large anharmonicity in all directions, which provides a promising scheme for cooling quantum gases using external driving.

We present a parametric driving method to cool an ultracold Fermi gas in a crossed-beam optical dipole trap. This method selectively removes high-energy atoms from the trap by periodically modulating the trap depth with frequencies that are resonant with the anharmonic components of the trapping potential.

We present a cooling method for a cold Fermi gas by parametrically driving atomic motions in a crossed-beam optical dipole trap (ODT). Our method employs ...

High-speed Continuous-wave Stimulated Brillouin Scattering Spectrometer for Material Analysis

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as aqueous solutions and biomaterials, with fast acquisition times. Here, we discuss the assembly and operation of a Brillouin spectrometer that uses stimulated Brillouin scattering (SBS) to measure stimulated Brillouin gain (SBG) spectra of water and lipid emulsion-based tissue-like samples in transmission mode with &lt;10 MHz spectral-resolution and &lt;35 MHz Brillouin-shift measurement precision at &lt;100 ms. The spectrometer consists of two nearly counter-propagating continuous-wave (CW) narrow-linewidth lasers at 780 nm whose frequency detuning is scanned through the material Brillouin shift. By using an ultra-narrowband hot rubidium-85 vapor notch filter and a phase-sensitive detector, the signal-to-noise-ratio of the SBG signal is significantly enhanced compared to that obtained with existing CW-SBS spectrometers. This improvement enables measurement of SBG spectra with up to 100-fold faster acquisition times, thereby facilitating high spectral-resolution and high-precision Brillouin analysis of soft materials at high speed.

We describe the construction of a rapid continuous-wave-stimulated-Brillouin-scattering (CW-SBS) spectrometer. The spectrometer employs single-frequency diode-lasers and an atomic vapor notch-filter to acquire transmission spectra of turbid/non-turbid samples with high spectral-resolution at speeds up to 100-fold faster than those of existing CW-SBS spectrometers. This improvement enables high-speed Brillouin material analysis.

Recent years have witnessed a significant increase in the use of spontaneous Brillouin spectrometers for non-contact analysis of soft matter, such as ...

Infrared Degenerate Four-wave Mixing with Upconversion Detection for Quantitative Gas Sensing

We present a protocol for performing gas spectroscopy using infrared degenerated four-wave mixing (IR-DFWM), for the quantitative detection of gas species in the ppm-to-single-percent range. The main purpose of the method is the spatially resolved detection of low-concentration species, which have no transitions in the visible or near-IR spectral range that could be used for detection. IR-DFWM is a nonintrusive method, which is a great advantage in combustion research, as inserting a probe into a flame can change it drastically. The IR-DFWM is combined with upconversion detection. This detection scheme uses sum-frequency generation to move the IR-DFWM signal from the mid-IR to the near-IR region, to take advantage of the superior noise characteristics of silicon-based detectors. This process also rejects most of the thermal background radiation. The focus of the protocol presented here is on the proper alignment of the IR-DFWM optics and on how to align an intracavity upconversion detection system.

Here, we present a protocol to perform sensitive, spatially resolved gas spectroscopy in the mid-infrared region, using degenerate four-wave mixing combined with upconversion detection.

We present a protocol for performing gas spectroscopy using infrared degenerated four-wave mixing (IR-DFWM), for the quantitative detection of gas species ...

Low-cost Custom Fabrication and Mode-locked Operation of an All-normal-dispersion Femtosecond Fiber Laser for Multiphoton Microscopy

A protocol is presented to build a custom low-cost yet high-performance femtosecond (fs) fiber laser. This all-normal-dispersion (ANDi) ytterbium-doped fiber laser is built completely using commercially available parts, including $8,000 in fiber optic and pump laser components, plus $4,800 in standard optical components and extra-cavity accessories. Researchers new to fiber optic device fabrication may also consider investing in basic fiber splicing and laser pulse characterization equipment (~$63,000). Important for optimal laser operation, methods to verify true versus apparent (partial or noise-like) mode-locked performance are presented. This system achieves 70 fs pulse duration with a center wavelength of approximately 1,070 nm and a pulse repetition rate of 31 MHz. This fiber laser exhibits the peak performance that may be obtained for an easily assembled fiber laser system, which makes this design ideal for research laboratories aiming to develop compact and portable fs laser technologies that enable new implementations of clinical multiphoton microscopy and fs surgery.

A method is presented to build a custom low-cost, mode-locked femtosecond fiber laser for potential applications in multiphoton microscopy, endoscopy, and photomedicine. This laser is built using commercially available parts and basic splicing techniques.

A protocol is presented to build a custom low-cost yet high-performance femtosecond (fs) fiber laser. This all-normal-dispersion (ANDi) ytterbium-doped ...

Rapid Repetition Rate Fluctuation Measurement of Soliton Crystals in a Microresonator

Temporal solitons have attracted great interest in the past decades for their behavior in a steady state, where the dispersion is balanced by the nonlinearity in a propagation Kerr medium. The development of dissipative Kerr solitons (DKSs) in high-Q microcavities drives a novel, compact, chip-scale soliton source. When DKSs serve as femtosecond pulses, the repetition rate fluctuation can be applied to ultrahigh precision metrology, high-speed optical sampling, and optical clocks, etc. In this paper, the rapid repetition rate fluctuation of soliton crystals (SCs), a special state of DKSs where particle-like solitons are tightly packed and fully occupy a resonator, is measured based on the well-known delayed self-heterodyne method. The SCs are generated using a thermal-controlled method. The pump is a frequency fixed laser with a linewidth of 100 Hz. The integral time in frequency fluctuation measurements is controlled by the length of the delay fiber. For a SC with a single vacancy, the repetition rate fluctuations are ~53.24 Hz within 10 &#181;s and ~509.32 Hz within 125 &#181;s, respectively.

Here, we present a protocol to generate soliton crystals in a butterfly-packaged micro-ring resonator using a thermal tuned method. Further, the repetition rate fluctuations of a soliton crystal with a single vacancy are measured using a delayed self-heterodyne method.

Temporal solitons have attracted great interest in the past decades for their behavior in a steady state, where the dispersion is balanced by the ...

Optimizing Brillouin Optical Time-Domain Analyzers Based on Gain Spectrum Engineering

Demonstrated is a unique method for sensing performance enhancement in Brillouin optical time-domain analyzers (BOTDA). A Brillouin gain spectrum (BGS) is superimposed with two symmetric Brillouin loss spectra (BLS). This leads to a complex engineered spectrum shape that is more resistant to the sensing system noise. Instead of only one pump and probe interaction as in the conventional BOTDA setup, three optical probe waves are exploited, with one probe located in the BGS and the other two symmetrically in the BLS. Due to the resistance and insensitivity of the engineered spectrum shape to the noise, the sensing performance is enhanced by 60% and the measurand resolution is doubled.

A protocol for Brillouin optical time-domain analyzers based on gain spectrum engineering is presented. Enhancements in the sensing performance, including sensing range and measurand resolution are achieved and the excess Brillouin intensity noise is studied. The protocol introduces a new way to enhance distributed Brillouin sensing performance.

Demonstrated is a unique method for sensing performance enhancement in Brillouin optical time-domain analyzers (BOTDA). A Brillouin gain spectrum (BGS) is ...