Alan C. Nilsson

Frequency stability and offset locking of a laser-diode-pumped Nd:YAG monolithic nonplanar ring oscillator

The frequency stability of laser-diode-pumped, monolithic Nd:YAG solid-state unidirectional nonplanar ring oscillators was studied by heterodyne measurements. We obtained cw single-axial- and transverse-mode power of 25 mW at 1064 nm at a slope efficiency of 19%. Two independent oscillators were offset locked at 17 MHz with frequency fluctuations of less than +/-40 kHz for periods of 8 min.

Eigenpolarization theory of monolithic nonplanar ring oscillators

Diode-laser-pumped monolithic nonplanar ring oscillators (NPROs) in a applied magnetic field can operate as unidirectional traveling-wave lasers. The diode laser pumping, monolithic construction, and unidirectional oscillation lead to narrow linewidth radiation. Here, a comprehensive theory of the eigenpolarizations of a monolithic NPRO is presented. It is shown how the properties of the integral optical diode that forces unidirectional operation depend on the choice of the gain medium, the applied magnetic field, the output coupler, and the geometry of the nonplanar ring light path. Using optical equivalence theorems to gain insight into the polarization characteristics of the NPRO, a strategy for designing NPROs with low thresholds and large loss nonreciprocities is given. An analysis of the eigenpolarizations for one such NPRO is presented, alternative optimization approaches are considered, and the prospects for further reducing the linewidths of these lasers are briefly discussed. >

Pulse-probe measurements in the v 3 band of SF 6 at low temperature and low pressure

To improve understanding of multiple-photon absorption by polyatomic molecules, we have performed a series of experiments wherein a pulsed CO 2 laser irradiated 0.02-0.08 torr samples of SF 6 at 145 K. A CW probe laser monitored the time response of the induced absorption or transmission at many CO 2 laser lines that are in or near the ν 3 absorption band of SF 6 . The experiments covered a 40-fold fluence range and probe times out to 4 ms. We conclude that the absorbed laser radiation produces a nonthermal vibrational-energy distribution and that intermolecular vibrational-energy transfer is important at early times in redistributing the absorbed energy. We also discuss the influence of other processes on the induced spectrum.

Monolithic Nonplanar Ring Lasers: Resistance To Optical Feedback

The sensitivity of a monolithic, unidirectional nonplanar ring laser to optical feedback depends on the polarization eigenmodes of the resonator, which are complicated functions of the resonator geometry. Resonator geometries that increase the loss difference between the two directions of propagation around the ring improve the resistance of the lasers to optical feedback. Measurements on Nd:YAG nonplanar ring lasers having two different ring geometries are discussed. Currently, 1% optical feedback produces 10% reduction in useful output power for the more feedback-resistant oscillator, a tenfold improvement over previous designs.

Narrow-Linewidth Operation of Diode-Laser-Pumped Nonplanar Ring Oscillators

The search for gravity waves, improved tests of relativity theory, advances in high resolution spectroscopy, and optical frequency standard development impose stringent requirements on the linewidth and frequency stability of lasers. Most efforts to produce narrow linewidth lasers have focused on He-Ne, dye, argon ion, or semiconductor lasers. These lasers exhibit free-running linewidths ranging from tens of kilohertz to several gigahertz and thus require wideband servo techniques for narrow linewidth operation [1]. Diode-laser-pumped monolithic solid-state lasers, on the other hand, can have free-running linewidths of a few kilohertz [2, 3], which makes them attractive candidates for narrow linewidth operation using low bandwith servo techniques. The short-term free-running stability is attributed to the small size and rigidity of the monolithic laser, which makes the optical cavity resistant to acoustical excitation, and to the low noise and efficiency of the diode laser pumping. Of particular interest are the diode-laser-pumped monolithic NonPlanar Ring Oscillators (NPROs) that overcome the problems of spatial hole burning and sensitivity to optical feedback inherent in linear cavity lasers [3, 4, 5]. Here we present our current NPRO design and explain its properties, discuss our recent narrow linewidth results obtained by locking a pair of diode-laser-pumped Nd:GGG NPROs to an optical cavity, and speculate about future developments.

Diode Pumped Solid-State Laser Oscillators for Spectroscopic Applications

Solid state laser development has been paced by the improvement of pumping sources. From the helical lamps used to pump the early Ruby lasers, to the linear arc and pulsed flashlamps used to pump Nd:YAG lasers, solid state laser pump sources have improved steadily in power and efficiency. The latest development is pumping solid state lasers with diode lasers and diode laser arrays. The development of high power, efficient, long lived diode lasers promises a revolution in solid state laser technology.