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Method of Determining Semiconductor- Laser Facet Reflectivity after Reflectance Modification


Optically Controlled Laser, Gain Quenched Laser Logic

Technical Challenge:

The reflectance of the output facets (mirrors) of a semiconductor laser can be modified using many techniques. The challenge is to determine the final reflectivity after reflectance modification, under real-world conditions. Typically surface reflectance measurement techniques direct an optical "probe" beam on to the surface and measure changes in the probe beam as it reflects off of the surface. The changes in the probe beam as it reflects from the surface are then used to calculate the reflectance of the surface.

Semiconductor-laser facets are extremely small (on the order of 5 microns high or less) therefore it is difficult to use standard surface reflectance measurement methods. When the lasers are integrated using microelectronics fabrication techniques, the laser facets are typically created by a process that forms the facet on the inner edge within an etched well. Currently, there is no reflectance measuring technique using a probe beam that can direct the probe beam onto the extremely small surface of the integrated laser facets (within the etched wells) to measure the reflectance of those facets as the reflectance is modified. The challenge is to be able to get quantified values of reflectance for the laser facets as the reflectance of those facets are modified, without using an external optical probe beam.


Typical semiconductor-lasers have two facets (mirrors). This technique uses changes in semiconductor-laser threshold current to calculate reflectivity changes for the laser facets. It provides the actual reflectance of the laser facets as "seen" by the laser, resulting in an accurate measure of facet reflectance. This technique can be applied for cases when one or both facet reflectances are modified. It can also be applied to iterative reflectance changes to the laser facets. The tools required to perform the measurements for this technique are: an optical power meter and a system to record the laser output power as a function of input current. These are tools typically required in the fabrication processes for fabricating semiconductor lasers. No external optical probe systems are required.

Demonstration Capability:

A demonstration is not available.

Potential Commercial Application(s):

In the manufacturing of semiconductors lasers.

Patent Status:

Issued- United States Patent Number 6,541,288

Reference Number: 1231

If you are interested in exploring this technology further, please express your interest in writing to the:

National Security Agency
NSA Technology Transfer Program
9800 Savage Road, Suite 6541
Fort George G. Meade, Maryland 20755-6541


Date Posted: Jan 15, 2009 | Last Modified: Apr 20, 2010 | Last Reviewed: Apr 20, 2010