Research Terms
Researchers at the University of Central Florida have developed a tunable laser with broadband coherent output spectrum within the mid-infrared (IR) range using a chirped quasi-phase-matched optical parametric amplifier/difference frequency generator (CQPM OPA/DFG)-based design.
Technical Details
This novel system involves a non-mechanical method of changing the relative timing of a pump pulse versus the seed pulse. The temporal variation varies the spatial/temporal overlap location of the spectrally narrow pump pulse over the spectrally broad seed spectrum taking place within the CQPM nonlinear medium. The overlap position regulates the phase-matched, seed pulse portion as the signal in the OPA or the seed for DFG.
Piezo-electric fiber stretchers are used to vary the relative pulse timing, thus enabling the output tuning from the OPA or DFG without using any moving parts. Fiber-coupled optical amplitude and/or phase modulators can also be included in either the pump or signal channels to provide control over the optical duty cycles as well as provide fine pulse control.
The University of Central Florida invention is a low-cost laser system that can achieve intense (1–10 GW) to super-intense (10 GW-1 TW) peak power pulses in the difficult-to-achieve long-wavelength (?>5 µm) mid-IR (MIR) spectral range. With such capabilities, the UCF Coherent Subharmonic Optical Parametric Amplifier (CSOPA) system enables new areas, including attosecond science and tabletop laser-driven particle accelerators for medical applications, including physical therapy.
Existing techniques for generating intense, ultrafast long-wavelength MIR pulses typically offer a conversion efficiency from near-IR to MIR of less than 1 percent. The techniques also require large, complicated laser facilities. Though another method provides high conversion efficiency, broad bandwidth, and preserves the coherence of the MIR output pulses, it delivers only low-energy pulses (1-10 nJ). The UCF invention offers a solution to all these issues.
Technical Details
The UCF invention is a coherent subharmonic optical parametric amplifier (CSOPA) laser system and method. The CSOPA uses a single intense input pump pulse, one or more passes through a nonlinear crystal, and does not require a resonator. As a result, subharmonic MIR pulses of much higher peak power are achievable. The energy conversion efficiency from the first pulse to the subharmonic wavelengths may exceed 50 percent due to: 1) the total photon recycling and 2) the non-dissipative nature of parametric conversion. A CSOPA requires precise control of the relative phases of the first pulse and the subharmonic pulse, which is achievable using an adjustable time delay such as a piezoelectric actuator.
In some embodiments, the CSOPA includes one or more amplifiers to amplify at least some of the pump pulses before the beam combiner. Any number or types of amplifiers are usable in the configuration, such as a chirped pulse amplifier (CPA), an optical parametric amplifier (OPA), or an optical parametric chirped-pulse amplifier (OPCPA). Also, the CSOPA may include multiple amplification stages. For instance, the CSOPA may consist of one or more pre-amplifiers and one or more main-stage or power amplifiers.
In one example application, the laser source includes a carrier envelope phase (CEP)-stabilized femtosecond laser amplifier providing phase-stabilized femtosecond input pulses with relatively high pulse energies (1-10 mJ or greater). The frequency divider is a sub-harmonic optical parametric generation (OPG) crystal.
Partnering Opportunity
The research team is looking for partners to develop the technology further for commercialization.
Ultra-broadband mid-infrared frequency combs produced by optical subharmonic generation, Quantum Electronics Volume 52, Number 4, 307-312 (2022).
