Coherent light generators – Particular active media – Semiconductor
Reexamination Certificate
1999-02-25
2002-02-12
Davie, James W. (Department: 2881)
Coherent light generators
Particular active media
Semiconductor
Reexamination Certificate
active
06347106
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to improvements in optoelectronic devices, such as laser diodes, light emitting diodes, semiconductor optical amplifiers, vertical cavity laser diodes, etc., and more specifically, the invention uses a highly thermally conductive (HTC) dielectric in optoelectronic devices.
2. Description of Related Art
Heat generation in any electronic semiconductor device is almost always deleterious to the device performance. The reason for this is basically the heat tends to “smear” or broaden the electron energy distribution and increase the decay rate of free carriers that contribute to the gain. The net effect in optoelectronic devices is that the optical gain decreases significantly with temperature. In devices such as laser diodes, light emitting diodes and optical amplifiers, these thermal effects can be catastrophic. The most common way to solve the problem is to conduct the heat away to a heat sink that is approximately at the ambient temperature.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide a highly thermally conductive layer for use in an optoelectronic device.
The present invention uses a highly heat conductive layer in combination with or in the vicinity of optical waveguides in active semiconductor components. The thermally conductive layer enhances the conduction of heat away from the active region, which is where the heat is generated in active semiconductor components. In the invention, this layer is placed so close to the optical region that it may also function as a waveguide. This layer then can cause the active region to be nearly the same temperature as the ambient or heat sink. However, the semiconductor material itself should be as temperature insensitive as possible and therefore the invention combines a highly thermally conductive dielectric layer with improved semiconductor materials to achieve an overall package that offers improved thermal performance. The semiconductor materials include InGaAs strained quantum wells on GaAs substrates and AlGaInAs/InGaAs quantum wells on InP substrates. Advances in the types of semiconductor materials and the dielectric materials may be applied to this invention. Also, these materials can be used for improving thermal issues on vertical cavity surface emitting lasers (VCSELs) and other optoelectronic devices where thermal generation and low heat conduction is significant.
The highly thermally conductive dielectric in this invention serves two basic functions. First, it provides a lower index material than the semiconductor device so that certain kinds of optical waveguides may be formed, e.g., a ridge waveguide. The second and most important function, as it relates to this invention, is that it provides a significantly higher thermal conductivity than the semiconductor material, which is the principal material in the fabrication of various optoelectronic devices. One goal of the invention is to operate these devices without thermoelectric coolers. Normally, the optoelectronic devices need some kind of temperature control in order to operate properly in an optical communications system. The temperature control apparatus is usually cumbersome and adds significant complexity to the system.
An embodiment of the present invention comprises the use of a highly thermally conductive dielectric as the material used in one or both of the mirrors in the design of a vertical cavity semiconductor laser (1.3-1.6 &mgr;m wavelength of operation). In the case of long-wavelength vertical cavity laser diodes, heat generation is a significant detriment to the successful operation of the laser. By using a highly thermally conductive dielectric Bragg mirror, heat from the active region can be quickly conducted to the heat sink, and thus for a given operating current, the operating temperature of the device can be significantly reduced.
The uses of the invention include: 1) fiber optic communication devices: lasers, high intensity light emitting diodes, and optical amplifiers for telecommunications, networking, or data transport within a system area network; 2) high sensitivity detection of optical signals for field deployment, etc.; 3) DOD fly by fiber and avionics; and 4) any optoelectronics where thermal performance is a significant issue and thermoelectric (TE) coolers are not appropriate. The above devices have numerous military and commercial applications in communications, sensors, surveillance and storage.
REFERENCES:
patent: 5974068 (1999-10-01), Hideto et al.
Deri Robert J.
Dijaili Sol P.
Goward William
Patterson Frank G.
Petersen Holly
Davie James W.
The Regents of the University of California
Thompson Alan H.
Wooldridge John P.
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