Design considerations for a high power, ultrabroadband optical parametric chirped-pulse amplifier

Abstract

A conceptual design of a high power, ultrabroadband optical parametric chirped-pulse amplifier (OPCPA) was carried out comparing nonlinear crystals (LBO and BBO) for 810 nm centered, sub-7.0 fs pulses with energies above 1 mJ. These amplifiers are only possible with a parallel development of kilowatt-level OPCPA-pump amplifiers. It is therefore important to know good strategies to use the available OPCPA-pump energy efficiently. Numerical simulations, including self- and cross-phase modulation, were used to investigate the critical parameters to achieve sufficient spectral and spatial quality. At high output powers, thermal absorption in the nonlinear crystals starts to degrade the output beam quality. Strategies to minimize thermal effects and limits to the maximum average power are discussed.

Sub-20 fs μJ-energy pulses tunable down to the near-UV from a 1 MHz Yb-fiber laser system

“…For kHz systems, this is marginally acceptable, but for MHz repetition rates such a strong TPA not only decreases the pump intensity but also leads to a high thermal load. A significant thermal load in the crystal will lead to a dramatic increase of the local temperature [23,30], a change in the phase matching, and eventually the destruction of the crystal. Consequently, for high repetition rates the pump wavelength has to be increased to reduce TPA.…”

An optical parametric chirped-pulse amplifier for seeding high repetition rate free-electron lasers

“…The above results demonstrate the feasibility of 112 W femtosecond OPCPA in burst mode with a duty cycle of 8 × 10 −3 , where no heating effects were observed. Recent measurements of absorption coefficients of BBO and LBO [13] and calculations [31] have demonstrated the feasibility of much higher powers up to 1 kW in continuous mode. Therefore, presently, the limits placed on high power OPCPA are determined by the power output of the OPCPA-pump.…”

“…For the following HGHG simulations (section 5), seeding will be examined at three frequencies-720 nm, 800 nm, and 900 nm-each with a pulse length of 30 fs. Conversion efficiencies, estimated using a fourth-order Runge-Kutta split-step Fourier algorithm [31], were found to be 5.8%, 9.3%, and 10.7% for 720, 800, and 900 nm, respectively. Scaling these values to the experimental value measured at 800 nm and using the results from figure 4(a), the expected energies for the TH are given in table 1.…”

Thermal properties of borate crystals for high power optical parametric chirped-pulse amplification

“…Such OPCPAs can be used as driving amplifiers for secondary sources in the field of attosecond technology and science [11]. For example, the Extreme Light Infrastructure -Attosecond Light Pulse Source (ELI-ALPS) in Hungary is planning a high power OPCPA operating at a repetition rate of 100 kHz with a pulse energy of up to 5 mJ and a pulse duration of sub-5 fs (1 mJ and sub-7 fs is planned in a first phase) [12,13]. At such high average powers, however, the absorption of optical power within the crystals cannot be neglected.…”

“…This leads to inhomogeneous heating of the nonlinear optical crystal and results in spatial temperature changes. Spatially inhomogeneous refractive index changes can occur, which lead to spatially varying phase-matching conditions, limiting the attainable average power, the spectral bandwidth [14], and the beam quality [13].…”