Abstract

The potential of high-energy sources within the mid-infrared region (3-8 μm) has garnered significant attention for diverse research and industrial applications. Millijoule pulses extending beyond 3 μm can facilitate the production of x-rays with photon energies in the keV range through high harmonic generation (HHG). These high-energy x-ray pulses enable the characterization of electron dynamics within molecules and condensed matter materials. Additionally, the atmospheric transmission window between 3-5 μm allows lasers within this spectral range to deliver energy efficiently to distant targets via optical filaments without divergence, highlighting promising prospects for defense applications. In contrast to laser amplifiers, which are restricted to several wavelengths within the mid-infrared spectral region, nonlinear optical effects allows the generation of pulses of similar energy but with a more adjustable spectrum. This flexibility makes amplification schemes, such as the Optical Parametric Chirped Pulse Amplifier (OPCPA), especially fitting for mid-Infrared applications. However, the efficiency of most existing systems operating above 3 μm is comparatively low due to the reliance on a near-infrared pump (0.75-1.4 μm). This thesis describes a novel tabletop OPCPA system, using ZnGeP2 pumped by a Ho:YLF chirped pulse amplifier (CPA) operating at 2 µm and seeded by intra-pulse difference frequency generation. The output energy and beam quality from the Ho:YLF laser are optimized by advancing the cooling system to reach lower operational temperatures, ensuring the quality of the OPCPA. Through the optimization of the ZGP's phase-matching bandwidth via a non-collinear configuration, and the enhancement of conversion efficiency with the aid of the top-hat pump, the OPCPA system can deliver 4-mJ, 50-fs pulses at a 1 kHz frequency. This system attains an unprecedented overall efficiency of 15% at this wavelength. The detection of harmonics up to the seventh order upon focusing the output in air substantiates the system's competence in conducting strong field experiments.

Notes

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Graduation Date

2023

Semester

Summer

Advisor

Chang, Zenghu

Degree

Doctor of Philosophy (Ph.D.)

College

College of Optics and Photonics

Department

Optics and Photonics

Degree Program

Optics and Photonics

Identifier

CFE0009902

Language

English

Release Date

February 2024

Length of Campus-only Access

None

Access Status

Doctoral Dissertation (Open Access)

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