Dr. D. T. Cassidy

Professor
Department of Engineering Physics

McMaster University
1280 Main Street West, Hamilton
Ontario, Canada  L8S 4L7

office: JHE/A323
email:  cassidy@mcmaster.ca
voice:  (905) 525-9140 x 24565
fax:    (905) 527-8409

B.Eng. (McMaster), M.Sc. (Eng.) (Queen's), Ph.D. (McMaster)

http://epic.mcmaster.ca/foswiki/bin/view/Main/DanielCassidy

Research Interests

Physics and Applications of III-V Materials and Devices

Devices based on III-V materials such as AlGaAs and InGaAsP semiconductor diode lasers are used in optical communication systems. Many of the operating characteristics of the devices are not well understood even though the devices are used extensively in the telecommunications industry. It is the object of the research programme to study the physics and applications of III-V materials and devices and to use the accumulated knowledge and experience to explain the operating characteristics and to find new applications.

Much of the work uses two technologies that were and are being developed in the research group: degree of polarization (DOP) of luminescence and short-external-cavity (SXC) modules. These technologies enhance the ability of the research group to make contributions.

With the DOP technique, the strain fields owing to, e.g., growth, processing, metallisation, die bonding, and single dislocations can be mapped quickly. There are few, if any, research groups that have this capability. Thus, the effects of strain on device performance can be determined and means to improve device performance suggested.

The luminescence from quantum wells is highly polarized. We have shown that the DOP of luminescence from quantum wells is a sensitive measure of the physical characteristics of the quantum well. Thus quantum wells can be characterized by the DOP of luminescence and the information gained by the characterization may be used to understand aspects of growth and performance of quantum well devices.

With the SXC technology, the spectral output of diode lasers can be controlled (i.e., the laser can be forced to run single mode on any of the modes near the gain peak). This allows for investigation of the wavelength dependence of ,e.g., the modulation bandwidth of diode lasers, the line width of lasers, and the nonlinear gain parameter. SXC lasers can also be used to construct sensors and to perform spectroscopy. The sensor work typically involves development of a system including source, optics, modulation/demodulation scheme, detection, signal processing electronics and algorithm, as necessary and application of the system to a relevant problem. We use a custom designed diffractive optical element as the feedback element for the external cavity lasers. The spectral properties of devices has been a continuing interest and recently has led to work on gain-coupled DFB lasers.

We design, fabricate, characterize and use lasers with broad gain peaks for operation over extended spectral intervals. The work on design, fabrication, and understanding of broad gain peak lasers is interesting for the physics of operation that is obtained and for the development of sources.

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Publications

D.T. Cassidy, S.K.K. Lam, B.Lakshmi, and D.M. Bruce, " Strain mapping by measurement of the degree of polarization of photoluminescence", Appl. Opt., submitted June 2003 for publication.

M.A. Fritz and D.T. Cassidy, "Diode laser bonding", IEEE Trans. on Components and Packaging Technology, accepted June 2003 for publication.

S.K.K. Lam, R.E. Mallard, and D.T. Cassidy, "Analytical model for saturable aging in semiconductor lasers", J. Appl. Phys., to be published in August 2003.

G.B. Morrison and D.T. Cassidy, "A probability-amplitude transfer-matrix method for calculating the distribution of light in semiconductor lasers", IEEE J. Quantum Electron. 39, 431-437 (2003).

S.C. Woodworth, D.T. Cassidy, and M.J. Hamp, "Experimental analysis of a broadly tunable InGaAsP laser with compositionally varied quantum wells", IEEE J. Quantum Electron. 39, 426-430 (2003).

G.B. Morrison and D.T. Cassidy, "A model for the above threshold spectra of truncated well distributed feedback lasers", IEEE J. Quantum Electron. 39, 426-430 (2003).

D.T. Cassidy, "Spatially-resolved and polarization-resolved photoluminescence for study of dislocations and strain in III-V materials", Mater. Sci. Eng. B91-92, 2-9 (2002).

S.C. Woodworth, D.T. Cassidy, and M.J. Hamp, "Sensitive absorption spectroscopy by use of an asymmetric multiple-quantum-well diode laser in an external cavity", Appl. Opt. 40, 6719-6724 (2001).

G.B. Morrison, D.T. Cassidy, and D.M. Bruce, "Facet phases and sub-threshold spectra of DFB lasers: spectral extraction, features, explanations, and verification", IEEE J. Quantum Electron. 37, 762-769 (2001).

D. Lisak, D.T. Cassidy, and A.H. Moore, "Bonding stress and reliability of high power GaAs-based lasers", IEEE Trans. on Components and Packaging Technology, submitted March 2000.

M.J. Hamp and D.T. Cassidy, "Critical design parameters for engineering broadly tunable asymmetric multiple quantum well lasers", IEEE J. Quantum Electron., to be published in August 2000.

G.B. Morrison and D.T. Cassidy, "Improving the ability of a distributed feedback laser transfer-matrix model to fit spectra from distributed feedback lasers", IEEE Photon. Technol. Lett., to be published in July 2000.

G.B. Morrison and D.T. Cassidy, "A probability-amplitude transfer matrix model for distributed feedback laser structures", IEEE J. Quantum Electron. 36, 633-640 (2000).

M.J. Hamp, D.T. Cassidy, B.J. Robinson, Q.C. Zhao, and D.A. Thompson, "Effect of barrier thickness of the carrier distribution in asymmetric multiple quantum well InGaAsP lasers", IEEE Photon. Technol. Lett. 12, 134-136 (2000).

G.B. Morrison, D.M. Adams, and D.T. Cassidy, "Extraction of gain parameters for truncated well gain-coupled DFB lasers", IEEE Photon. Technol. Lett. 11, 1566-1568 (1999).

D.T. Cassidy and M.J. Hamp, "Diffractive optical element used in an external feedback configuration to tune the wavelength of uncoated Fabry-Pérot diode lasers", J. Mod. Opt. 46, 1071-1078 (1999).

M.J. Hamp, D.T. Cassidy, B.J. Robinson, Q.C. Zhao, and D.A. Thompson, "Nonuniform carrier distribution in asymmetric multiple-quantum-well InGaAsP laser structures with different number of quantum wells", Appl. Phys. Lett. 74, 744-746 (1999).

B. Lakshmi, D.T. Cassidy, and B.J. Robinson, , "Anisotropic interfacial strain in InP/InGaAs/InP quantum wells", J. Appl. Phys. 84, 5739-5742 (1998).

M.J. Hamp, D.T. Cassidy, B.J. Robinson, Q.C. Zhao, D.A. Thompson, and M. Davies, "Effect of barrier height on the uneven carrier distribution in asymmetric multiple-quantum-
well InGaAsP lasers", IEEE Photon. Technol. Lett. 10, 1380-1382 (1998).

A. Gupta, G.C. Weatherly, D.T. Cassidy, and D.M. Bruce, "Characterization and modelling of the strain fields associated with InGaAs layers on V-grooved InP substrates", J. Appl. Phys. 82, 6016-6023 (1997).

X. Zhu, D.T. Cassidy, M.J. Hamp, D.A. Thompson, B.J. Robinson, Q.C. Zhao, and M. Davies, "1.4µm InGaAsP-InP Strained Multiple-Quantum-Well Laser for Broad-Wavelength Tunability", IEEE Photon. Technol. Letters. 9, 1202-1204 (1997).

X. Zhu and D.T. Cassidy, "Modulation spectroscopy with a semiconductor diode laser by injection-current modulation", J. Opt. Soc. Am. B., 14, 1945-1950 (1997).

D.M. Adams, D.T. Cassidy and D.M. Bruce, "Scanning photoluminescence technique to determine the phase of the grating at the facets of gain-coupled DFB's", IEEE J. Quantum Electron. 32, 1237-1242 (1996).

X. Zhu and D.T. Cassidy, "Liquid detection using InGaAsP semiconductor lasers with multiple short-external cavities", Appl. Opt. 35, 4689-4693 (1996).

B. Lakshmi, D.T. Cassidy and B.J. Robinson, "Quantum well strain and thickness characterization by degree of polarization", J. Appl. Phys. 79, 7640-7645 (1996).

A. Nguyen and D.T. Cassidy, "Flexure-mounted external cavity for single mode operation of semiconductor diode lasers", Rev. Sci. Instrumen. 66, 4458-4460 (1995).

J. Yang and D.T. Cassidy, "Strain measurement and estimation of photoelastic effects and strain-induced optical gain change in ridge waveguide lasers", J. Appl. Phys. 77, 3382-3387 (1995).

J.E. Hayward and D.T. Cassidy, "Nonlinear gain and the spectral output of short-external-cavity 1.3 µm InGaAsP semiconductor diode lasers", IEEE J. Quantum Electron. 30, 2043-2050 (1994).