C. C. Bradley

Instrumentation for the stable operation of laser diodes

We have developed a constant current supply and a temperature control circuit that can be used for frequency‐stable operation of laser diodes. These instruments can stabilize laser diode injection current and temperature to better than ±1 μA and ±0.3 mK, respectively, over time periods exceeding 1 h. We have excited the Li(2S↔2P) transition with a red‐light‐emitting laser diode and find that our instrumentation stabilizes the laser frequency to within ±10 MHz over a period exceeding 1 h.

Difference-frequency generation in AgGaS2 by use of single-mode diode-laser pump sources

We explored the suitability of visible III–V single-mode cw diodes for difference-frequency generation of tunable infrared radiation by mixing a red single-mode cw III–V diode laser with a tunable single-frequency cw Ti:sapphire laser in AgGaS2. More than 1 μW of cw tunable, infrared (λ ≈ 5 μm), narrow-band coherent radiation was generated with type I noncritical phase matching. The wavelength and output-power characteristics of this novel tunable all-solid-state laser source are described, and we demonstrate the applicability of the source to high-resolution molecular spectroscopy by obtaining a test spectrum. The feasibility of a more compact solid-state cw laser spectrometer based on the mixing of two single-mode diode lasers (808 and 690 nm) as pump sources in AgGaS2 is shown (infrared power generated ≈3 nW).

Bose–Einstein condensation of lithium

Bose-Einstein condensation of 7Li has been studied in a magnetically trapped gas. Because of the effectively attractive interactions between 7Li atoms, many-body quantum theory predicts that the occupation number of the condensate is limited to about 1400 atoms. We observe the condensate number to be limited to a maximum value between 650 and 1300 atoms. The measurements were made using a versatile phase-contrast imaging technique. We discuss our measurements, the current theoretical understanding of BEC in a gas with attractive interactions, and future experiments we hope to perform.

Laser cooling of lithium using relay chirp cooling

We demonstrate a chirp-cooling technique that uses a laser with multiple FM sidebands to slow lithium atoms from initial velocities of as much as 1880 m/s to final velocities near zero. Compared with the use of a single sideband, this multisideband technique significantly reduces FM bandwidth requirements and provides a greater flux of slowed atoms.