BrightLock™

We have achieved spectrum control from a monolithic diode laser with an internal grating, thereby eliminating the need for any external optical elements and reducing cost and increasing overall device robustness. The performance of the semiconductor laser with an internal grating differs fundamentally from a conventional high power diode without the internal grating or from a conventional diode with an external grating.

First, the 0.2 nm FWHM spectrum is significantly narrower than the 1.5-4.5 nm FWHM typically achieved in conventional high power diode lasers without a grating. The narrower spectrum increases pumping efficiency for any medium with narrow absorption peaks, and the repeatability of the spectrum allows laser designers more flexibility in their system architectures.

Another major difference between devices with an internal grating and conventional diode lasers is the lower wavelength - temperature coefficient. For conventional diode lasers, this coefficient is 0.3nm/degC while for devices with internal gratings, it is 0.08 nm/degreeC. This reduction in temperature sensitivity relaxes the requirement for thermal stabilization, enabling systems with reduced size and weight.

A third major difference is the significantly improved center wavelength accuracy achieved in the manufacturing process. Conventional pump lasers are typically provided with a +/- 3 nm center wavelength tolerance due to growth control and uniformity factors, as well as effects related to bonding stress. Slightly narrower spreads (~+/- 2 nm) are achievable at higher cost by selecting from the wavelength distribution of the pumps.

On the other hand, the wavelength of devices with internal gratings is determined by the period of the grating which can be controlled accurately and is unaffected by growth uniformity. This enables +-0.5 nm spread in devices from growth to growth and wafer to wafer. The improved accuracy of center wavelengths from the manufacturing process results in a reduction in the systems thermal management requirements, increased system compactness and reduced weight. Moreover, because the diode lasers are also operated over a narrower temperature range, the lifetime of the diodes is expected to be more uniform in a given laser design.