Optical Parametric Chirped-pulse Amplification System Research Articles

Development of a high-contrast, high-peak power, Ti:Sapphire/OPCPA laser system

We report on a high-contrast, high-peak power laser system, which combines both conventional laser amplification and optical parametric chirped pulse amplification (OPCPA) techniques. By employing an OPCPA system after a regenerative amplifier, we have enhanced the prepulse contrast by six orders of magnitude. A prepulse contrast of better than 4.4 × 10−11 has been measured with a high-energy broadband pulse of 24 mJ at a 10 Hz repetition rate from the OPCPA system. With a subsequent four-pass Ti:sapphire amplifier, we have achieved an amplified energy of 279 mJ and an ultrashort recompressed amplified pulse duration of 23.5 fs. We also discuss the basic design aspects and present our preliminary experimental investigations for higher energy operation to a multijoule.

Energy and average power scalable optical parametric chirped-pulse amplification in yttrium calcium oxyborate

Optical parametric chirped-pulse amplification (OPCPA) in nonlinear crystals has the potential to produce extremes of peak and average power but is limited either in energy by crystal growth issues or in average power by crystal thermo-optic characteristics. Recently, large (7.5 cm diameter x 25 cm length) crystals of yttrium calcium oxyborate (YCOB) have been grown and utilized for high-average-power second-harmonic generation. Further, YCOB has the necessary thermo-optic properties required for scaling OPCPA systems to high peak and average power operation for wavelengths near 1 microm. We report what is believed to be the first use of YCOB for OPCPA. Scalability to higher peak and average power is addressed.

Optical switching and contrast enhancement in intense laser systems by cascaded optical parametric amplification

Optical parametric chirped-pulse amplification (OPCPA) can be used to improve the prepulse contrast in chirped-pulse amplification systems by amplifying the main pulse with a total saturated OPCPA gain, while not affecting the preceding prepulses of the seed oscillator mode-locked pulse train. We show that a simple modification of a multistage OPCPA system into a cascaded optical parametric amplifier (COPA) results in an optical switch and extreme contrast enhancement that can completely eliminate the preceding and trailing oscillator pulses. Instrument-limited measurement of a prepulse contrast ratio of 1.4 x 10(11) is demonstrated from COPA at a 30 mJ level.

Nonlinear temporal pulse cleaning of a 1-μm optical parametric chirped-pulse amplification system

We demonstrate the technique of cross-polarized wave (XPW) generation at 1 μm with a 310-fs optical parametric chirped-pulse amplification system at the millijoule level. We show an improvement of the temporal contrast by three orders of magnitude with an energy transmission of 22%. Additionally, we report that XPW generation preserves the beam spatial quality and shortens the pulse duration by a factor of 31/2, resulting in a peak power transmission of ∼35%.

Degenerated optical parametric chirped-pulse amplification with cesium lithium borate

A gain amplifier for degenerated optical parametric chirped-pulse amplification (OPCPA) with lithium triborate and cesium lithium borate (CLBO) crystals was demonstrated in a near-collinear configuration. The signal gain of the final energy amplifier with CLBO was approximately 6. After compression, the 123 fs pulse duration was obtained. Compared with potassium dihydrogen phosphate, it is confirmed that CLBO is more effective as a nonlinear crystal in a final power amplifier for terawatt or petawatt OPCPA systems. To our knowledge, this is the first demonstration of OPCPA with CLBO.

Prepulse-free, multi-terawatt, sub-30-fs laser system

We have built a prepulse-free, multi-terawatt, ultrashort pulse laser system, which combines both conventional laser amplification and optical parametric chirped pulse amplification (OPCPA) techniques. By employing an OPCPA system after the regenerative amplifier in a Ti:sapphire chirped pulse amplification laser chain, we have dramatically enhanced the prepulse contrast by 6 orders of magnitude. A prepulse contrast of better than 4.4 x 10-11 has been measured with a high energy broadband pulse of 24 mJ at 10 Hz repetition rate from the OPCPA system. Using a subsequent four-pass Ti:sapphire amplifier, we have achieved an amplified energy of 279 mJ and an ultrashort recompressed amplified pulse duration of 23.5 fs, corresponding to the peak powers for OPCPA and four-pass amplifier of 0.5 TW and 5.9 TW, respectively.

Observation of nonlinear optical phenomena in air and fused silica using a 100 GW, 1.54 μm source

A 100-GW optical parametric chirped-pulse amplifier system is used to study nonlinear effects in the 1.54 mum regime. When focusing this beam in air, strong third-harmonic generation (THG) is observed, and both the spectra and efficiency are measured. Broadening is observed on only the blue side of the third-harmonic signal and an energy conversion efficiency of 0.2% is achieved. When propagated through a 10-cm block of fused silica, a collimated beam is seen to collapse and form multiple filaments. The measured spectral features span 400-2100 nm. The spectrum is dominated by previously unobserved Stokes emissions and broad emissions in the visible.

Dispersion Analysis and Compensation of Collinear OpticalParametric Chirped Pulse Amplification Systems

In an optical parametric chirped pulse amplification (OPCPA) lasersystem, residual phase dispersion should be compensated as much aspossible to shorten the amplified pulses and improve the pulse contrastratio. Expressions of orders of the induced phases in collinear opticalparametric amplification (OPA) processes are presented at the centralsignal wavelength to depict a clear physics picture and to simplify thedesign of phase compensation. As examples, we simulate two OPCPAsystems to compensate for the phases up to the partial fourth-orderterms, and obtain flat phase spectra of 200-nm bandwidth at 1064 nm and90-nm at 800 nm.

High and Stable Conversion Efficiency Obtaining inSingle-Stage Multi-Crystal Optical Parametric Chirped PulseAmplification System

An optical parametric chirped-pulse amplification system isdemonstrated to provide 32.9% pump-to-signal conversion efficiency.Special techniques are used to make the signal and pump pulses matchwith each other in both spectral and temporal domains. The broadband9.5-mJ pulses are produced at the repetition rate of 1 Hz with the gainof over 1.9×108. The output energy fluctuation of 7.8% isachieved for the saturated amplification process against the pumpfluctuation of 10%.

High-power optical parametric chirped-pulse amplifier system with a 155??m signal and a 1064??m pump

We have designed and built a chirped-pulse parametric-amplifier system that utilizes a 10 Hz, 300 ps, Nd:YAG pump laser system; a 1.575 microm fiber oscillator and amplifier as the signal source; and rubidium titanyl phosphate and potassium titanyl arsenate nonlinear crystals. We obtained 260 fs, 30 mJ pulses centered at 1.550 microm, representing a gain of > 10(9) and a peak power of 100 GW. To our knowledge, these are the highest energy and peak power pulses ever produced in the 1.5-2.0 microm region

Precision short-pulse damage test station utilizing optical parametric chirped-pulse amplification

The next generation of high-energy petawatt (HEPW)-class lasers will utilize multilayer dielectric diffraction gratings for pulse compression, due to their high efficiency and high damage threshold for picosecond pulses. The peak power of HEPW lasers will be determined by the aperture and damage threshold of the final dielectric grating in the pulse compressor and final focusing optics. We have developed a short-pulse damage test station for accurate determination of the damage threshold of the optics used on future HEPW lasers. Our damage test station is based on a highly stable, high-beam-quality optical parametric chirped-pulse amplifier (OPCPA) operating at 1053 nm at a repetition rate of 10 Hz. We present the design of our OPCPA system pumped by a commercial Q-switched pump laser and the results of the full system characterization. Initial short-pulse damage experiments in the far field using our system have been performed.

Design of a highly stable, high-conversion-efficiency, optical parametric chirped-pulse amplification system with good beam quality

An optical parametric chirped-pulse amplifier (OPCPA) design that provides 40% pump-to-signal conversion efficiency and over-500-mJ signal energy at 1054 nm for front-end injection into a Nd:glass amplifier chain is presented. This OPCPA system is currently being built as the prototype front end for the OMEGA EP (extended performance) laser system at the University of Rochester's Laboratory for Laser Energetics. Using a three-dimensional spatial and temporal numerical model, several design considerations necessary to achieve high conversion efficiency, good output stability, and good beam quality are discussed. The dependence of OPCPA output on the pump beam's spatiotemporal shape and the relative size of seed and pump beams is described. This includes the effects of pump intensity modulation and pump-signal walk-off. The trade-off among efficiency, stability, and low output beam intensity modulation is discussed.

High-conversion-efficiency optical parametric chirped-pulse amplification system using spatiotemporally shaped pump pulses.

High-conversion-efficiency, high-stability optical parametric chirped-pulse amplification is demonstrated with a spatiotemporally shaped pump laser system. Broadband 5-mJ pulses are produced at a 5-Hz repetition rate with a pump-to-signal conversion efficiency of 29% and energy stability better than 2% rms. To our knowledge this is the highest conversion efficiency and stability achieved in an optical parametric chirped-pulse amplification system.

Numerical studies of characteristics and the design of 1PW optical parametric chirped pulse amplifier for the “Shenguang-Ⅱ” facility

In this paper, the characteristics of optical parametric chirped pulse amplification(OPCPA) are numerically studied by a computer- The infection of the group velocity mismatch, the phase-velocity mismatch, and the cubic nonlinearity in the process of amplification has been discussed respectively- The comparison between the OPCPA and the chirped-pulse amplification(CPA) is made, such as of the mechanism of amplification, the synchronization, the red-shift phenomenon, the gain-narrowing effect, and so on- To realize the fast ignition of inertial confinement fusion, we have designed an OPCPA system for the “Shenguang-Ⅱ” facility, which can generate pulse with a duration as short as 50fs and a power of multi-petawatt-

OPTIMIZED DESIGN OF A SYSTEM OF GENERATING TERAWATT LASER PULSES BY USE OF OPTICAL PARAMETRIC CHIRPED PULSE AMPLIFICATION

Using the numerical method, an optimized design is presented for the generation of peak powers up to ～60 TW with pulse duration ～25 fs using an optical parametric chirped pulse amplifier (OPCPA) pumped by the high-power Nd:glass laser. The OPCPA system consists of an LBO preamplifier and an LBO power amplifier. The numerical simulation results demonstrate that this system can scale the pulse energy at nanojoule level to the joule level and generate terawatt pulses. So it provides great po-tential to efficiently produce and amplify very short femtosecond laser pulses, and can be regarded as a step toward generating petawatt laser pulses using optical parametric chirped pulse amplifiers pumped by powerful nanosecond systems.

Design of a multi-petawatt optical parametric chirped pulse amplifier for the iodine laser ASTERIX IV

A theoretical design is presented for the generation of peak powers up to /spl sim/5 PW and focused intensities higher than 10/sup 23/ Wcm/sup -2/ with pulse duration /spl sim/20 fs using an optical parametric chirped pulse amplifier (OPCPA) pumped by the high-power iodine laser Asterix IV. These values represent an improvement to the existing Asterix laser by a factor of /spl sim/1000 and at least LOO 000 for the output peak power and focused intensity, respectively. The OPCPA system consists of two LBO preamplifiers and a KDP power amplifier and is pumped by the laser third-harmonic output (438 nm, 500 ps, 500 J). Numerical simulations show that saturation within the OPCPA can be effectively used to counteract the bandwidth narrowing effects brought about by the temporal variation of the pump pulse intensity. The results demonstrate that the OPCPA represents a powerful technique for the generation of ultrahigh powers with iodine lasers at a level currently not achievable with any other approach, and proves that the iodine system is particularly suitable as an OPCPA pump source.