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GaAs QUANTUM WELL Q-SWITCHED LASER GROWN ON PATTERNED SUBSTRATES

IP.com Disclosure Number: IPCOM000034934D
Original Publication Date: 1989-May-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 2 page(s) / 47K

Publishing Venue

IBM

Related People

Harder, CS: AUTHOR [+4]

Abstract

Q-switched semiconductor lasers are of interest in optical fiber communication systems as sources for very short pulses at high bit rates. Q-switched lasers have a gain section (GS) and a modulator section (MS) that modulates the optical absorption of the laser cavity and therefore switches the laser on and off. High speed operation requires an extremely low MS capacitance. Disclosed is a Q-switched laser in which the bandgap energy of the MS is 20 - 40 meV higher compared to the GS. The required reverse bias voltage to modulate the laser is more negative and thus the capacity lower than in conventional semiconductor Q-switched lasers.

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GaAs QUANTUM WELL Q-SWITCHED LASER GROWN ON PATTERNED SUBSTRATES

Q-switched semiconductor lasers are of interest in optical fiber communication systems as sources for very short pulses at high bit rates. Q-switched lasers have a gain section (GS) and a modulator section (MS) that modulates the optical absorption of the laser cavity and therefore switches the laser on and off. High speed operation requires an extremely low MS capacitance. Disclosed is a Q-switched laser in which the bandgap energy of the MS is 20 - 40 meV higher compared to the GS. The required reverse bias voltage to modulate the laser is more negative and thus the capacity lower than in conventional semiconductor Q-switched lasers. GaAs quantum wells (QWs) grown by molecular beam epitaxy (MBE) on ridged substrates are thicker on a narrow ridge (NR) than on a wide ridge (WR) because of surface diffusion of Ga atoms during growth, and consequently have smaller effective bandgaps. This effect is used in the design of the laser structure shown in the figure. A (100)-GaAs substrate is patterned in the (011) direction, the ridge width varying between NR and WR sections. During the subsequent MBE growth of the layers forming the laser structure, a narrower bandgap gain section (GS) is formed on the NR and a wider bandgap modulator section (MS) on the WR. Post growth processing consists of forming a waveguide in the MS and a laser diode using standard techniques. In summary, by using channeled substrate...