Tunable cw Pb0.98 Cd0.02S diode lasers emitting at 3.5 μm: Applications to ultrahigh-resolution spectroscopy

Abstract

Continuously tunable cw diode lasers that produce narrow‐line (1‐ to 10‐MHz linewidth) radiation in the 3.5‐μm region have been fabricated from Pb_0.98Cd_0.02S. Lasers operating at 10–20 K produced more than 1 mW of cw power distributed among several modes which could be tuned continuously > 1 cm⁻¹ by adjusting the laser current. A spectral range of 30 cm⁻¹ could be covered over the full operating range. Ultrahigh‐resolution (10⁻⁵ cm⁻¹) spectra of H₂CO have been obtained to demonstrate the potential application of these lasers to the identification of organic molecules by spectroscopy of their C–H stretch absorption bands.