Iain T. McKinnie

HIGHLY EFFICIENT SINGLE-LONGITUDINAL-MODE BETA-BAB2O4 OPTICAL PARAMETRIC OSCILLATOR WITH A NEW CAVITY DESIGN

A new coupled-cavity design for single-longitudinal-mode operation of an optical parametric oscillator (OPO) is presented. The OPO is based on a beta-BaB(2)O(4) crystal and is pumped by the third harmonic of a Nd:YAG laser. With this design, we achieved single-longitudinal-mode operation of the OPO with a decrease in the threshold and an increase in external efficiency compared with those of a conventional grazing-incidence OPO. A mathematical model that describes the mode spacings for this cavity is given.

Tunable infrared laser sources for DIAL

Broadly tunable infrared laser sources are of interest for a variety of applications including differential absorption lidar, differential scattering lidar, multi-spectral detection and imaging, hard target identification and discrimination, optical communications in poor visibility conditions, and spectroscopy. For chemical sensing applications, sources are particularly sought in the mid-wave infrared (MWIR) and long-wave infrared (LWIR) spectral regions. A variety of laser and nonlinear optical devices have been demonstrated that access these wavelengths. In particular, CTI is developing novel, tunable, narrow linewidth transmitters for coherent and direct detection lidar measurement applications. An example is a multi-watt Cr:ZnSe laser that is tunable over the 2.1 to 2.8 micrometers wavelength region. This laser has been used to pump-tune optical parametric oscillators (OPOs) that are broadly tunable across the MWIR and LWIR. We are also developing tunable Yb lasers that can be used to pump OPOs that emit signal beams in the eyesafe 1.55 micrometers region while generating idler beams that access the 3 to 4 micrometers MWIR band. This paper describes these sources.

Frequency locking of a pulsed single-longitudinal-mode laser in a coupled-cavity resonator

The performance of a novel resonator that couples a grazing-incidence and a linear cavity is reported. The coupling secures single-longitudinal mode, TEM(00), higher-efficiency and lower-threshold operation. By use of Ti:sapphire as the gain medium, a slope efficiency of 23% and a 100-nm tuning range are reported. A model is explained that fully predicts the mode behavior of the resonator and that can be used to optimize the cavity for single-mode operation. We have developed computer control of the cavity, which is simple in design and is used to lock the <200-MHz bandwidth mode to +/-40 MHz. A 4.8-GHz scan has also been demonstrated.

Tunable high-repetition-rate visible solid-state lasers based on intracavity frequency doubling of Cr:forsterite

High-repetition-rate solid-state lasers broadly tunable in the red-orange and infrared spectral regions are reported. Wavelengths between 590 and 670 nm and between 1170 and 1360 nm have been generated by gain-switched Cr:forsterite lasers incorporating intracavity frequency doubling in KTP. Broadband, tuned, and narrow-band systems operating at repetition rates between 1 and 20 kHz have been developed. Maximum visible output power of 40 mW was achieved by frequency doubling of a narrow-band infrared laser, corresponding to a fundamental to second-harmonic conversion efficiency of more than 30%.

Tunable, single axial mode LiF:F2− laser

Abstract We have developed a gain-switched room temperature single axial mode LiF:F 2 − laser using a coupled narrowband resonator. The resonator uses a classic four-prism achromatic beam expander/Littrow grating configuration, augmented with a dichroic mirror that defines a coupled resonator with: (1) reduced threshold and higher efficiency, and (2) dramatically increased axial mode separation for enhanced mode selectivity. One etalon was then sufficient to achieve single axial mode output with MHz bandwidth and an energy conversion efficiency of 5.5%, significantly higher than previously reported for narrowband LiF:F 2 − lasers where only a bandwidth of 300 MHz had been achieved. The single longitudinal mode laser was tunable in single mode between 1120 and 1200 nm. A coupled cavity model was developed to explain the experimentally observed mode structure, and to allow similar coupled resonators to be optimised for other vibronic laser media.

Dual-band Cr:ZnSe laser pump-tuned OPOs

CrZnSe laser pump-tuned ZnGeP2 and CdSe optical parametric oscillators (OPOs) that simultaneously output in the mid-wave infrared and long-wave infrared are described. OPO optical-to-optical conversion efficiencies as high as 45% have been achieved.

The first-order hyperpolarizabilities of some charge transfer conjugated molecules with high transmission in the far red

Abstract The first-order hyperpolarizabilities, β, of a number of novel merocyanine compounds bearing electron donor and acceptor groups at opposite ends of the molecules have been determined using hyper-Rayleigh scattering. The values of β increased with increasing strength of the electron acceptors and extent of conjugation including the molecular moiety linking the donor and acceptor groups. Furthermore, the non-aromatic 1,4 dihydropyridyl donor gives a greater β value than the benzothiazole donor.

Highly achromatic, narrow linewidth distributed feedback dye laser pumped by a multimode laser

Highly achromatic operation of a computer-optimized distributed feedback dye laser is reported. Linewidths of between 320 and 500 MHz, a factor of up to 100 less than the pump laser linewidth, have been measured across a scanning range of 70 nm. The dependence of the laser linewidth on pump laser parameters such as linewidth and energy has also been studied. The wavelength dependence of the laser linewidth was well represented by a computer model, and the measured threshold was close to the value predicted by a rate equation model. A conversion efficiency of 20% was obtained. >

High-energy solid-state Raman laser based on Barium Nitrate crystal for near IR and visible spectral range

A Barium Nitrate Raman laser pumped by a Q-switched Nd:YAG laser has been developed. The Raman output was doubled in LBO with conversion efficiencies as high as 43%. The main limitations of this laser have been identified as the shot to shot output stability and high beam divergence. High beam divergence complicates collimation and therefore subsequent frequency doubling due to the low acceptance angle values for most nonlinear crystals. Beam homogeneity of the Raman laser is very sensitive to the quality of the Raman medium.

Single frequency, coupled cavity chromium forsterite laser

Narrow bandwidth operation of a gain-switched chromium (IV) laser is reported for the first time. Near transform-limited single longitudinal mode pulses have been obtained from a novel coupled-cavity laser. The laser output was tunable across a 100nm wavelength range. Excitation was provided by the fundamental of a Q-switched Nd:YAG laser.