Method for reducing amplitude noise in multi-wavelength modelocked semiconductor lasers

• Main Authors: Delfyett, Peter J, Mielke, Michael M
• Format: Patent
• Language: English
• Published: 10.02.2004

Multiwavelength generation lasers have been increasingly demonstrated over the past several years. For example, the subject invention assignee as been at the forefront of developing multiwavelength modelocked semiconductor diode lasers. See for example, Shi et al. "Four-wavelength, 10-GHZ picosecond pulse generation from an active modelocked single-stripe diode laser," Conference proceeding presentation on May 18-23, 1997, OSA Technical Technical Digest Series Vol. 11, Conference on Lasers and Electro-optics (CLEO), 1997; and Mielke et al. "60 channel WDM transmitter using multiwavelength modelocked semiconductor laser," , v 38 n 8 Apr. 11, 2002. P. 368-370. Wavelength division multiplexing (WDM) in telecommunication and data transmission systems increases system capacity by more fully taking advantage of the intrinsic bandwidth of installed optical fiber. Channel widths and spacings have been standardized so those necessary system components such as lasers and spectrally dispersive components can be designed for interoperability. Simultaneously, the data rate of individual channels is being pushed toward higher rates with approximately 10 Gbit standards (both Sonet and Ethernet) near deployment. Current architectures utilize a separate laser for each wavelength channel introducing complexity and cost issues. Significant research has been conducted to develop and assess potential multiwavelength sources for WDM systems. Multiple active device arrays of both laser diodes and vertical cavity surface emitting lasers (VCSELs) have been constructed and tested but problems with growth control toward exact spectral emission remain a concern. See Kudo, K., Furushima, Y., Nakazaki, T., Yamaguchi, M., "Multiwavelength microarray semiconductor lasers", , v 34 n 21 Oct. 15, 1998. P. 2037-2038. Continuum generation in optical fibers from high power pulsed sources followed by spectral filtering has been demonstrated but suffers from the need for the high power front end as well as the power inefficiency of discarding much of the generated spectrum in the filtering process. See Morioka, T., Mori, K., Kawanishi, S., Saruwatari, M., "Multi-WDM-channel, Gbit/s pulse generation from a single laser source utilizing LD-pumped super continuum in optical fibers", , v 6 n 3 March 1994. P. 365-368. Multiwavelength modelocked laser systems and methods for reducing intensity fluctuations and amplitude noise in each of the wavelength channels as well as manipulating the interwavelength phase coherence properties. The systems and methods can include lens, semiconductor optical amplifier, grating, cylindrical lens, rod lens and an approximately 7 nm MQW saturable absorber between mirrors for providing a laser cavity resonator for hybridly modelocked operation. Additional systems and methods can include two different positions for the saturable absorber inside the laser resonator which enables direction of the interwavelength phase coherence properties. Up to approximately 300 MHz optical pulse trains in each of up to approximately three channels can be generated. Combining gain flattening and noise suppression within the optical cavity of the modelocked laser can result in generating up to approximately 123 wavelength channels, each having up to approximately 6 Giga Hertz optical pulse trains.