Wideband Modulation and Tuning of Semiconductor Lasers Using Novel Quantum Well Structures
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.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jan 01, 1994
- Accession Number
- ADA379992
Entities
People
- Alwyn Seeds
- Xuan Huang
Organizations
- University of London