High-efficiency high-power solid-state CW visible lasers for large-format-display applications

摘要

High-efficiency (5%-10% wall-plug efficiency) high-power continuous-wave (CW) visible lasers have been developed for large-format-display applications (e.g., planetariums, visualization centers, etc.). Using an approach pioneered by Evans & Sutherland (E&S), a fiber based master-oscillator-power-amplifier (MOPA) architecture is employed to generate high power near-infrared (NIR) tunable lasers that are then converted to visible wavelengths in external enhancement nonlinear ring cavities. Depending on the wavelength generated, either second-harmonic generation or sum-frequency mixing (or both) in lithium triborate (LBO) are utilized to convert 1064 nm and/or 1550 nm to visible wavelengths, with NIR-to-visible optical-conversion efficiencies of 65%-95% routinely obtained. The resulting visible lasers are single-axial-frequency (FWHM bandwidth < 200 kHz) spatially pure (m~2 < 1.05) Gaussian beams, and are used as light sources in ultrahigh-resolution projectors manufactured by E&S. The current systems reliably produce 6 W of visible laser power at 448 nm, 532 nm, and 631 nm, with short-term CW operation yielding up to 18 W visible-laser output per color. Laser-induced damage (LID) on nonlinear-crystal facets is the primary limitation to long-term operation at visible powers > 6 W, and efforts are underway to increase crystal LID thresholds to allow reliable operation at greater power levels.