Accession Number:

ADA379992

Title:

Wideband Modulation and Tuning of Semiconductor Lasers Using Novel Quantum Well Structures

Descriptive Note:

Final rept.

Corporate Author:

LONDON UNIV (UNITED KINGDOM) DEPT OF ELECTRONIC AND ELECTRICAL ENGINEERING

Personal Author(s):

• Huang, Xuan
• Seeds, Alwyn

Report Date:

1994-01-01

Pagination or Media Count:

69.0

Abstract:

Angle modulation techniques enable analogue optical transmission systems to be realized which have dynamic ranges in excess of those possible with conventional intensity modulation direct detection IMDD links. Tunable semiconductor lasers are essential components for links employing optical frequency modulation OFM for enhanced dynamic range or dense wavelength division multiplex DWDM for multi-channel capability. They are also key components in many advanced sensor systems. Existing lasers use the forward bias carrier injection effect CIE to achieve tuning. Whilst this is a convenient technique for wavelength setting it suffers from severe limitations when fast tuning or modulation of the laser frequency is required. At low modulation frequencies the response is dominated by thermal effects, leading to a decrease in emission frequency with increasing carrier, whereas at high frequencies the response is dominated by plasma and band filling effects giving an increase in frequency with increasing current. The resulting overall frequency response typically vaiies by more than an order of magnitude from 0-1GHz accompanied by phase variations of up to pi radians. Equalizing such a response, even over a restricted frequency range, request complex networks that have to be optimized for the particular laser and its operating conditions. Improved uniformity of response has been obtained in multi- electrode distributed feedback DFB lasers by carefully adjusting the distribution of current between sections, but the high frequency response tends to be limited by current lifetime in the section biased below transparency to about 1GHz.

Descriptors:

• *QUANTUM WELLS
• *SEMICONDUCTOR LASERS
• HIGH FREQUENCY
• TUNABLE LASERS
• PLASMAS(PHYSICS)
• FREQUENCY MODULATION
• ELECTRODES
• ELECTRIC CURRENT
• LOW FREQUENCY
• DYNAMIC RANGE
• MULTICHANNEL
• PHASE SHIFT
• DISTRIBUTED AMPLIFIERS
• UNITED KINGDOM
• WAVELENGTH DIVISION MULTIPLEXING
• WIDE GAP SEMICONDUCTORS

Subject Categories:

• Lasers and Masers

Distribution Statement:

APPROVED FOR PUBLIC RELEASE