No abstract

Absorption spectroscopy in (3)He and (4)He has been performed with an InGaAs single-mode distributed Bragg reflection laser diode. The laser source provides as much as 120 mW of single-mode, single-frequency output in the 1083-nm region of the spectrum. Frequency tuning of the laser diode output by means of the junction temperature allows for mode-hop-free scanning of the entire 2(3)S-2(3)P manifold in both the (3)He and (4)He absorption spectra. The authors believe this to be the first report of semiconductor laser spectroscopy at this wavelength. Such a device will have significant applications in optical pumping, atomic cooling and trapping, fundamental nuclear studies, magnetometry, and gas dynamics.

A stable, low-noise, tunable, solid-state laser has been constructed for use in magnetometry. The system is designed specifically for applications in which a rugged, magnetically clean source is required. A La1−xNdxMgAl11O19 (LNA or LMA) laser crystal provides the 1083-nm radiation necessary for optical pumping of gaseous helium, the process on which our magnetometer design is based. Laser characteristics of the 0.5-W SDL 2432 laser-diode-pumped device consist of 112-mW free-running laser output near 1082 nm, a threshold of 35 mW, and an output power of up to 26 mW within a single longitudinal mode at the helium metastable resonance wavelengths, obtained by insertion of an intracavity solid étalon. The structure of the ‘‘hand-held’’ laser unit is presented with particular emphasis on the laser parameters required for low-noise operation of this source at the wavelengths of interest.

Several Nd:YAP lasers were constructed which could be broadly tuned in the 1083-nm region which includes the helium 23S-23P transition, using a Lyot filter and thin, uncoated etalons within the laser cavity. 1 W of power could be extracted at 1083 nm through a 1% transmitting output coupler. This laser beam was used to optically pump metastable 4He and 3He 23S helium atoms in a weak discharge cell, spin polarizing the metastable ensemble. In a 3He cell the polarization is transferred to the nuclear spin system. A 3He target cell at 0.3 Torr was polarized to 52% in a few minutes. We describe the application of this system to the design of polarized targets for experiments in nuclear physics.

A high power, diode-pumped Er:YAG laser platform is presented, which has been integrated into devices for soft as well as hard tissue applications. The highly efficient side pumping by qcw laser diodes allows easy power scalability and miniaturization proven by a portable fractional ablative laser system based on a 2 W laser. The high repetition rate of up to 1 kHz combined with low energy pulses generates high thermal impact and consequently strong skin rejuvenation. Furthermore a laser for hard tissue applications with up to 15 W average output power at repetition rates up to 2 kHz is presented. The good beam quality allows coupling to 200 µm fibers and the variable pulse duration of 1 to 200 µs ensures precise and fast treatments.