Evaluation of white-light generation as possible seed for a mid-infrared optical parametric chirped pulse amplifier

Abstract

White-light spectra of different crystals, based on 1030-nm intense pump pulses have been investigated in order to derive a near-infrared seed for mid-infrared generation. Among ten crystals, YAG (yttrium aluminium garnet), KGW (potassium gadolinium tungstate) and YVO4 (yttrium orthovanadate) exhibit the most suitable properties for supercontinuum generation with high efficiency for spectral broadening as well as high tolerance to optical damage. Numerical simulations of laser induced filamentation, a dynamic balance between self-focusing and plasma defocusing resulting in supercontinuum generation, have been carried out to interpret and support our results theoretically. The simulations are in fair agreement with experimental results and they support the finding that low-bandgap materials like YVO4, YAG and KGW seem to be better suited than high-bandgap materials, like fused silica and fluorides.

Popular Abstract

Nowadays, mid-infrared (MIR) light (2 μm to 10 μm) has provided excellent view of atoms, molecules and solids and opened up many applications, such as the observation of atmospheric reactions and non-invasive surgery. In particular, absorption spectroscopy benefits significantly from MIR sources because a large number of molecule absorption lines exist in the MIR region, which therefore is also called molecular fingerprint region. For example, water has very strong absorption lines near 3 μm, from which biomedical applications benefit, such as tissue surgery and imaging on dermatology.


In this project, we aim at the generation of MIR pulses from a near-infrared pump at 1030 nm. The MIR generation is based on a nonlinear optical process where the medium exhibits nonlinear response to the input light. One of these processes is called difference frequency generation (also called optical parametric amplification) where the energy from a higher frequency wave can be converted into a lower frequency wave, e.g. in our project, by mixing the output of the 1030-nm pulsed laser with light at 1500-nm, resulting in 4 μm MIR light. The wave at 1500 nm is called signal wave (seed) and the resulting wave at 4 μm is called idler wave.

The thesis work focuses on the generation of the signal wave at 1500 nm which should be derived from the pump radiation at 1030 nm. The generation of the signal wave is based on another set of nonlinear interactions between a laser pulse and a medium, such as self-focusing, self-phase modulation and plasma defusing, that lead to a super broadband spectrum (supercontinuum) covering our desired range (1.4 μm to 1.6 μm). Several materials have been investigated for the preparation of supercontinuum generation. The experimental results indicate that YAG (yttrium aluminium garnet), KGW (potassium gadolinium tungstate) and YVO4 (yttrium orthovanadate) are the most suitable materials, with high efficiency for spectral broadening as well as high tolerance to optical damage. The experimental results are supported by simulations which were performed based on a nonlinear pulse propagation model.

• author: Lu, Chuang
• supervisor: Cord Arnold
• organization: Department of Physics; Nuclear physics
• course: FYSM60 20162
• year: 2017
• type: H2 - Master's Degree (Two Years)
• subject: Physics and Astronomy
• keywords: nonlinear linear optics, ultrafast optics, Mid-infrared generation, near-infrared, Optical parametric amplification, Optical Parametric Chirped-pulse Amplification, supercontinuum generation, white-light generation, laser induced filamentation, Dispersion-scan, nonlinear propagation
• publication/series: Lund report on Atomic Physics
• language: English
• id: 8906730
• date added to LUP: 2017-05-14 14:27:44
• date last changed: 2017-05-14 14:27:44