Grating External Cavity Diode Lasers with Broad Tunable Range and Narrow Spectral Linewidth for High-Resolution Spectroscopy

Abstract

A grating external cavity technique is used to improve the poor spectral qualities of commercially available semiconductor lasers in order to realize high-resolution spectroscopy. We describe a method of coating an anti-reflector onto the front facet of semiconductor lasers to suppress the intrinsic laser oscillation. The coated laser operates in an external cavity with a Littrow-mounted diffraction grating. The spectral linewidth of the resultant laser system is confirmed to be less than 250 kHz, and the system can be scanned over 25 nm. In order to demonstrate its improved tunability, we observed three resonance lines of two alkali-metal atoms, Rb-D2 (780.0 nm), K-D1 (769.9 nm) and K-D2 (766.5 nm), without replacing the laser chip.

Electromagnetic Wave Chaos in Gradient Refractive Index Optical Cavities

“…To resolve peaks in T ͑v͒ corresponding to individual eigenmodes would therefore require a laser with linewidth and tuning precision of ϳ1 MHz. Linewidths of this order have been reported in tunable lasers [15]. Alternatively, we could measure T as a function of temperature at fixed v. Thermal expansion would change the size of the cavity and thereby alter the optical path lengths of the periodic rays, with transmission maxima occurring for quantized values of L͞l.…”