Compact continuous wave tunable infrared lasers and method therefor

Abstract

A bulk, quasi-periodic phase-matched difference-frequency (DFG) process in field-poled LiNbO.sub.3 bulk crystal permits continuous tunability of the output radiation in the 3.0-4.1 .mu.m wavelength range through grating rotation. DFG in QPM-LiNbO.sub.3 crystal, carried out using a Nd:YAG laser and a high power semiconductor laser at the quasi-phased matching (QPM) degeneracy point, results in an ultra wide 0.5 .mu.m acceptance bandwidth, permitting crystal rotation-free wavelength tuning of 4.0-4.5 .mu.m, with 0.2 mW output power at 4.5 .mu.m.

Description

BACKGROUND OF THE INVENTION1. Field of the InventionThe present invention relates generally to mid-range infrared (IR) laser sources. More specifically, the present invention relates to mid-range IR laser sources produced by difference-frequency generating (DFG) optical circuits using bulk crystals.2. Description of the Background ArtMid-range IR (2-4 .mu.m) sources are of interest in the field of spectroscopy, pollution monitoring, electronic warfare (EW) applications, etc. Adequate sources in this wavelength range generally do not exist. Filament, or black body emitters, have low, uncollimated power and provide poor spectral resolution. Semiconductor laser sources require low temperature operation and have limited tunability.Tunable laser-like sources are generally obtained from optical parametric oscillators (OPO's), which have been available for some time. However these usually have kilowatt power thresholds, which require complicated Q-switched lasers. Often, these lasers must ...

AI Technical Summary

Benefits of technology

An object according to the present invention is to produce a laser system applying a difference-frequency generation (DFG) process which provides a narrow bandwidth resultant output responsive to fixed and variable inputs. According to one aspect of the invention, a bulk, quasi-periodic phase-matched difference-frequency generation (DFG) process in field-poled LiNbO.sub.3 bulk crystal permits continuous tunability of the output radiation in the 3.0-4.1 .mu.m wavelength range through grating rotation.

Problems solved by technology

Filament, or black body emitters, have low, uncollimated power and provide poor spectral resolution.

Semiconductor laser sources require low temperature operation and have limited tunability.

However these usually have kilowatt power thresholds, which require complicated Q-switched lasers.

OPO's are usually thermally tuned, often up to 180 degrees C; thus tuning is slow.

Characteristic outputs have been low (.apprxeq.50 .mu.W) and these outputs not widely tunable due primarily to limitations of bifringence phase matching.

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