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Browse Prior Art Database

Fabrication for a Tunable Monochromatic Injection Laser

IP.com Disclosure Number: IPCOM000077354D
Original Publication Date: 1972-Jul-01
Included in the Prior Art Database: 2005-Feb-25
Document File: 3 page(s) / 62K

Publishing Venue

IBM

Related People

Ludeke, R: AUTHOR [+2]

Abstract

This device provides a tunable, coherent light source of cw or pulsed radiation over a spectral range 6200-5600 angstroms, which is not readily covered by any other tunable laser.

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Fabrication for a Tunable Monochromatic Injection Laser

This device provides a tunable, coherent light source of cw or pulsed radiation over a spectral range 6200-5600 angstroms, which is not readily covered by any other tunable laser.

The underlying principle of the device is the extension of the recombination- radiation-bandwidth from a few hundred angstroms in a GaAs diode to a few thousand angstroms in a diode made with a graded gap junction of Ga(x)Al(1- x)As, for instance. Such a diode D is shown in Fig. 1. The device is constructed in such a way that the alloy concentration y of Ga increases in the direction of the arrow, being 0.66 at the top of the device and 1.0 near the bottom. For the latter case, the wavelength of the recombination radiation is around 8600 angstroms while for the former case, around 6200 angstroms.

To make a tunable laser source, diode D is coated on one face with a suitable antireflection coating 1 and placed in an external dispersive cavity with a rotatable grating 2, as shown in Fig. 2. A suitable lens 3 is adjusted to optimize feedback and hence initiate lasing. Tuning is obtained by rotating grating 2 about axis 4.

Diode D may be fabricated by overgrowing a GaAs substrate with a suitably doped epitaxial layer of Ga(x)Al(1-x)As of rapidly changing composition. The compositional change should occur over a range of 100-300 mu meters. The wafer is then cut and an appropriate dopant diffused into the cut pieces to form the pN junction. The individual diodes are cleaved from this material. However, there is a drawback to this simple structure, namely, a "shorting" effect in the lower energy, GaAs rich region of the junction. This effect can drastically reduce the carriers available for radiative recombination...