At Waterloo, we are developing a high power, short pulse, two-color, Yb:fiber amplifier system to generate the long wavelength (<15μm) side of the molecular fingerprint spectral region, by difference frequency mixing the two colors. This spectral region is important for trace gas detection of explosives. As an example, it has been shown that the strong spectroscopic signatures of a peroxide-based explosive triacetone triperoxide (TATP) occur between 15 and 20 μm. To date, we have achieved a tuning range from 16 to 20 μm with a maximum average power of 1.7 mW. On the short wavelength side, the two colors would need to be pulled further apart, which requires a higher power seed to beat the amplified spontaneous emission that appears at the gain peak of the amplifiers between the two seed colors. On the long wavelength side, we are limited to 20 μm by the transparency region of the nonlinear crystals. We would like to find new nonlinear materials that have transparency from 1 to 30μm. If we could generate wavelengths from 15 to 30 μm with sufficient power, we could extend the spectral region to also cover 8 to 15μm by frequency doubling the longer wavelengths. We are currently working on replacing bulk optics in the system with fiber based optical elements to select the wavelengths as well as stretch and recompress the pulses in order to make the system compact and stable.
The University of Waterloo, partnered with key industry players, Photonics Research Ontario and the Ontario government, launched Ontario's first diploma-level photonics program to re-skill scientists and engineers. The Education Program for Photonics Professionals (EP3) offers the basics of a university level Optics education. The next step is to provide the courses at distance.
Pump-probe spectroscopy of molecular systems requires high average power, short pulse, mid-infrared sources. Today OPO deliver wavelengths up to 4 µm and THz systems supply wavelengths beyond 20 µm. To achieve tunable wavelengths in between these two regions, the signal and idler beams of the OPO can be difference frequency mixed again. This two-step nonlinear process necessarily leads to average power much less than the OPO pump, which is typically a 1 W Ti:sapphire laser. In this paper, we report initial experimental results of two-wavelength amplification in a Yb-doped DCF fiber. Yb:fibre amplifiers have been shown to deliver short pulses at average power levels of up to 20 W .The goal of the work is to generate high average power (>1W) pump and signal beams for difference frequency generation at around 15 µm.
A schematic of the experimental is shown in Fig.1. A photonics crystal fiber is pumped by a mode-locked Ti:Sapphire laser to create supercontinuum, from which we can select the two seed wavelengths by using a standard zero dispersion grating line that has been adapted to have individual mirrors in the focal plane for the two different colours. The Yb:fibre is pumped by a 915nm diode laser. As shown in Fig. 2, at a pump power of 2.1 W, 500 gain was achieved yielding 150 mW total power(1055 and 1095 nm).
References:1. D. Nickel et al, Opt. Commun. 190, 309 (2001)
The University of Waterloo, partnered with key industry players, Photonics Research Ontario and the Ontario government, has launched Ontario’s first diploma-level photonics program to re-skill scientists and engineers. The Education Program for Photonics Professionals (EP3) offers the basics of a university level Optics education, but in a manageable timeframe and format for the working professional.
A short pulse will develop temporal sub-structures as it self- focuses. We show how these substructures lead to both the catastrophic expansion of the spectrum and the remarkable beam stability against self-focusing.