Jason K. Brasseur

High average power diamond Raman laser

We report a pulsed Raman laser at 1193 nm based on synthetic diamond crystals with a record output power of 24.5 W and a slope efficiency of 57%. We compared the performance of an anti-reflection coated crystal at normal incidence with a Brewster cut sample. Raman oscillation was achieved at both room temperature and under cryogenic operation at 77 K. Modeling of these experiments allowed us to confirm the value of Raman gain coefficient of diamond, which was found to be 13.5 ± 2.0 cm/GW for a pump wavelength of 1030 nm.

Diode-pumped nonresonant continuous-wave Raman laser in H2 with resonant optical feedback stabilization.

We demonstrate a nonresonant cw Raman laser pumped by an optically locked diode laser at 790 nm that produces cw Stokes (1178-nm) and coherent anti-Stokes (595-nm) emission. Considering the modest pump powers, relative low cost, and predicted spectral purity, we expect that frequency downconversion of tunable diode lasers through stimulated Raman scattering will provide an attractive source for remote sensing, spectroscopic, and atomic physics applications. The Stokes laser threshold is 240+/-19muW pump power, and emission is observed over a roughly 10-nm range by adjustment of the optical locking feedback phase. Photon-conversion efficiency rises throughout the pump-power region, with a peak value of 15+/-2% .

High power 7-GHz bandwidth external-cavity diode laser array and its use in optically pumping singlet delta oxygen

Spectral bandwidth of a diode laser array is narrowed to 7 GHz FWHM by using a thick volume Bragg grating. Total output power reaches 13.5 W cw, of which 86% is in the 7-GHz band.

85% power conversion efficiency 975-nm broad area diode lasers at − 50°C, 76 % at 10°C

Optimized single stripe 975-nm broad area devices deliver 76% power conversion efficiency at 10degC. Cooling the material leads to 85% efficiency at -50degC. External differential quantum efficiency is the dominant term.

2.3-kW continuous operation cryogenic Yb:YAG laser

We present our recent developments in high-power, high-efficiency cryogenic Yb:YAG laser systems. Specifically, we will discuss our 2.3-kW master oscillator power amplifier (MOPA) which has shown optical wall-plug efficiencies above 30-% (diode-driver input to optical output). This laser system has been operated for long run times with continuous wave and pulsed output formats. The beam quality factor, M2, of the MOPA has been measured to be less than 2 and it is currently limited by the master oscillator. We are working to improve the devices beam quality and output power. In addition, we have demonstrated an all-cryogenic Yb:YAG laser that produced 29 W of optical power. Use of cryogenic diode laser pumps represents our next step towards achieving greater than 50% efficient high-power laser systems.

Phase and frequency stabilization of a pump laser to a Raman active resonator

In this paper, we describe how to phase and frequency stabilize a continuous wave (CW) Raman laser. We model and measure the transfer function of a high-finesse cavity filled with a Raman active gas. In addition, we model the time dependence of the temperature-induced oscillations inherent to the CW Raman laser. The results set the minimum feedback-loop bandwidth at about 100 kHz to adequately suppress the temperature-induced oscillations. The required bandwidth is an order of magnitude larger than the empty resonator case.

Highly efficient, resonant Raman molecular iodine laser.

A highly efficient 1.3-microm molecular iodine Raman laser is demonstrated. Multiwavelength output powers of 600 mW and photon-conversion efficiencies of 78% are demonstrated for a 532-nm pump source. Single-wavelength output powers of 480 mW and photon-conversion efficiencies of 67% are also realized. A simple thermal lensing model is used to optimize the pump and Stokes mode sizes.

Correcting an astigmatic, non-Gaussian beam

An off-axis spherical mirror is used to correct an astigmatic, non-Gaussian beam from a pulsed, frequency-doubled Nd:YAG laser. The beam is then spatially filtered by a series of two pinholes to make the beam near Gaussian.

High power Raman diamond laser

We developed a cryogenically cooled Yb:YAG laser as the pump beam for a pulsed Raman laser based on CVD grown diamond crystals. The Q-switched cryogenic Yb-doped YAG 1030 nm pump laser delivered 340 W at 40 kHz with diffraction-limited beam quality, with an optical efficiency of 80%. The record average power of 24.5 W was generated from the Raman laser at 1193 nm. Modeling of the performance confirmed the corresponding Raman gain coefficient, 13.5 cm/GW. The laser was operated at room temperature and under cryogenic cooling at 77 K, with equal performance.

Development of a non-contact center thickness optical metrology system

The last place an optics manufacturer wants to physically touch a lens is at the center. However, this is precisely what is currently done to measure center thickness of lenses. Using contact methods, the question is not whether the optic is damaged, it is whether the resulting damage is acceptably low. At Bridger Photonics, we have proven the feasibility of a non-contact center thickness metrology system to address this need. The apparatus uses a technique similar to swept-frequency optical coherence tomography to measure both physical thickness and optical thickness. From these measurements, the group index of refraction can also be determined. Moreover, the phase index can be determined, given the Sellmeier coefficients. In this presentation, we will report our demonstrated measurement range of 75 mm optical thickness (larger possible), as low as 20 nm precision, and group index of refraction determined to better than 5 parts is 105. We believe the metrology system resulting from these proof-of-principle demonstrations will be a valuable tool for precision optics manufacturing.