Browse Prior Art Database

Laser Diode Performance Improvement

IP.com Disclosure Number: IPCOM000061953D
Original Publication Date: 1986-Aug-01
Included in the Prior Art Database: 2005-Mar-09
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Davie, NR: AUTHOR

Abstract

The laser monitor photodiode commonly employed for laser power control is located at the laser rear facet. The photodiode's indication of power emitted at the laser front facet varies. A method to remove the variation of the percentage power seen by the monitor diode at the laser rear facet and simultaneously to minimize the laser feedback noise is described herein.

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Laser Diode Performance Improvement

The laser monitor photodiode commonly employed for laser power control is located at the laser rear facet. The photodiode's indication of power emitted at the laser front facet varies. A method to remove the variation of the percentage power seen by the monitor diode at the laser rear facet and simultaneously to minimize the laser feedback noise is described herein.

A high-frequency, typically 50 MHz to 200 MHz, current is superimposed with the DC bias current nominally employed for laser optical power generation. As a result of the high- frequency varying current, the laser's longitudinal operating mode is made to change at a rate significantly in excess of the operating data frequency in an optical recording application. The feedback reflectance to the monitor photodiode, when changing at that rate, lacks the coherence to significantly modify the laser operating condition.

Referring to Fig. 1, the laser diode 8 is operated by current from three sources: a read current source 10 providing a DC current at a level appropriate for read bias and write bias power requirements, a laser write driver 12 for the purpose of providing the additional current pulses necessary to write optical data, and a high-frequency oscillator 14 to provide an alternating current source for laser diode 8. Feedback control of read current and laser write driver functions is accomplished with a monitor photodiode 16. The monitor photodiode 16 is packaged...