Dean Street,Bangor LL 57 1 UT
email : alan@sees.bangor.ac.uk
The initial aims of this project had ,on the insistence of 'expert' referees and the relevant EPSRC committee , been restricted to theoretical work on the creation of intersubband population inversion in semiconductor quantum wells. Shortly after the award of the grant the successful operation of intersubband quantum cascade lasers by Faist and Capasso at AT&T was announced - almost two years after the initial identification of this opportunity by the Principal Investigator at an EPSRC community meeting. The announcement of the quantum cascade laser vindicated the initial judgement of this investigator and provided justification for effecting a significant broadening of the scope of the project to consider structures where lasing action can be obtained , to study their operating characteristics and to evaluate their performance. The main results obtained in the course of this projects are as follows :
(i) Optical waveguide designs have been identified for improving intersubband laser performance.Waveguide design work has been undertaken , on an informal basis ,in support of experimental work being undertaken at Sheffield University.
(ii) Opportunities for utilising TE -polarisation intersubband transitions to facilitate vertical cavity intersubband lasers have been identified with prospects of exploiting microcavity effects to improve device operating characteristics.
(iii) Predictions have been made of THz direct current modulation bandwidth consequent to picosecond electron lifetimes in intersubband lasers.
(iv) Structures have been identified for exploiting near-infra-red intersubband transitions to deliver THz modulation bandwidths to meet rapidly-emerging optical communications systems requirements.
(v) The use of hole intersubband transitions to promote far-infra-red emission and lasing has been studied in detail.
A substantial part of the project output has already appeared in refereed archival journals and has been presented at a number of international and national conferences.It was disappointing to find that ,despite these achievements, 'expert' referees employed by EPSRC have frustrated efforts to maintain the momentum of the work on intersubband lasers at Bangor.
Project Publications
A. Full Journal Papers
1. P.S.SPENCER and K.A.SHORE , "Quantum well structures for intersubband semiconductor lasers", Int.Journal of Optoelectronics,10,393-400, 1996
2. P.S.SPENCER and K.A.SHORE, "Surface plasmon effects and waveguide properties of quantum cascade lasers", IEE Proc. Optoelectronics ,144,48-52,1997
3. P.S. SPENCER ,C .Y. L .CHEUNG and K. A .SHORE, " Sensitivity analysis of optical waveguide properties of quantum cascade semiconductor lasers",IEE Proc. Optoelectronics , 144,323-326, October 1997
4. C .Y. L .CHEUNG, P.S. SPENCER and K. A .SHORE, "Modulation bandwidth optimisation for unipolar inter-subband semiconductor lasers ",IEE Proc. Optoelectronics, 144,44-47, 1997
5. C .Y. L .CHEUNG and K.A.SHORE, " Self-consistent analysis of the direct-current modulation response of unipolar semiconductor lasers ",J. Mod Optics , 45,1219-1229, 1998
6. W. BATTY, and K.A. SHORE, " Normal incidence operation in n-type unipolar opto-electronic devices : TE intersubband transitions in conduction band quantum wells " , IEE Proc- Optoelectronics, 145,21-30, February 1998
7. C .Y. L .CHEUNG, P. PEES and K.A.SHORE, " Optical gain calculations for intersubband semiconductor lasers ",IEE Proc Optoelectronics , in preparation
8. W. BATTY, K. A. SHORE, B. E. COLE, J. M. CHAMBERLAIN and J. SINGLETON,"Hole Landau levels in [hkk]-grown quantum wells: calculations in the axial approximation ",J. Appl.Phys. (to be submitted)
9. W. BATTY, K. A. SHORE, B. E. COLE, J. M. CHAMBERLAINand J. SINGLETON,"Hole Landau levels in [hkk]-grown quantum wells beyond the axial approximation: Burt-Foreman hermitianisation, interface terms and k-linear hole subband splitting ", J. Appl. Phys. (in preparation)
10. CHEUNG, C .Y. L .and SHORE, K. A ., " Anticrossing effects in the design of intersubband semiconductor lasers ",in preparation
B. International Conference Presentations
11. K.A.SHORE , "Operating principles of inter-subband QW semiconductor lasers" Encuentro sobre semiconductor lasers", Invited Oral Paper, Facultad de Ciencias,Universidad de Cantabria, Santander ,Spain, June 1996
12. P.S.SPENCER and K.A.SHORE " Inhibiting surface plasmon effects in intersubband MIR semiconductor lasers", Poster Paper , IOP International conference on 'Mid-infrared Optoelectronics : Materials and Devices',Lancaster University, September 1996
13. C.Y.L.CHEUNG, P .S. SPENCER and K.A.SHORE, "Optimisation of maximum modulation bandwidth of inter-subband semiconductor lasers ",Poster Paper , IOP International conference on ' Mid-infrared Optoelectronics : Materials and Devices',Lancaster University, September 1996
14. C.Y.L CHEUNG, P.S.SPENCER and K. A .SHORE , " Modulation bandwidth predictions for intersubband quantum well semiconductor lasers " Optical Society of America, Integrated Photonics Research conference, Boston, Mass., USA,Oral Post-deadline paper PD-1,April 1996
15. C.Y.L CHEUNG, P.S.SPENCER and K. A .SHORE , " Analysis of the dynamical properties and modulation response of unipolar semiconductor lasers ", Optical Society of America, CLEO/QELS 97, Baltimore,Maryland USA, Oral Paper CThS2,May 1997
16. CHEUNG,C .Y. L. and SHORE, K .A," Carrier lifetime calculations and modulation response of intersubband semiconductor lasers ",SPIE,Photonics West'98, Conference on Physics and Simulation of Optoelectronic Devices, San Jose, CA, USA, Oral Paper 3283/48, January 1998
17. C.Y.L.CHEUNG,P.REES and K.A. SHORE," Optical gain calculations for near-infra-red intersubband semiconductor lasers ", Paper, CTuI57, CLEO Europe, Glasgow,1998
18. C.Y.L.CHEUNG,P.REES and K.A. SHORE," Quantum well structures for THz bandwidth near-infra-red unipolar semiconductor lasers ",6 th IEEE Terahertz Electronics conference, Leeds, 1998
C. National Conference Presentations
19. SHORE,K.A., SPENCER,P.S. and CHEUNG,C.Y.L. , "Threshold conditions and modulation properties of intersubband lasers "Quantum Optoelectronics Symposium , IOP CMMP'95, Liverpool December 1995
20. CHEUNG C.Y.L, SPENCER P.S. and SHORE K.A., "Modulation Bandwidth Predictions For Unipolar Intersubband Semiconductor Lasers", 10th Conference on Semiconductor and Integrated Optoelectronics (SIOE'96), Cardiff, April 1996
21. W. BATTY and K.A. SHORE, " Self-consistent calculations of population inversion in quantum cascade lasers ",IOP Condensed Matter and Material Physics Conference ( CMMP'96), York, December 1996
22. W. BATTY and K.A. SHORE," Burt-Foreman hermitianisation, interface terms and hole subband, zone centre, linear spin splitting" IOP Condensed Matter and Material Physics Conference ( CMMP'96), York,December 1996
23. BATTY,W. and SHORE,K.A.," Intersubband transitions in conduction band quantum wells : TE absorption and emission " , 11th Conference on Semiconductor and Integrated Optoelectronics (SIOE'97),Cardiff,March 1997
24. C Y L CHEUNG and K A SHORE, " Electron Lifetime Calculations and Lasing Properties of inter-subband semiconductor lasers " , 11th Conference on Semiconductor and Integrated Optoelectronics (SIOE'97),Cardiff,March 1997
25. W.BATTY and K.A.SHORE , " Normal incidence operation in n-type unipolar optoelectronic devices : TE intersubband matrix elements ", IOP National Quantum Electronics conference (QE'13) ,Cardiff,Wales, September 1997
26. C Y L CHEUNG and K A SHORE," Self-consistent analysis of the direct current modulation response of unipolar semiconductor lasers ",IOP National Quantum Electronics conference (QE'13) ,Cardiff ,Wales,September 1997
27. N.CINOSI, C.Y.L. CHEUNG and K.A.SHORE," Mode Transformations in Planar Self-similar Cantor Waveguide Structures ", 12th Conference on Semiconductor and Integrated Optoelectronics (SIOE'98) ,Aberdare Hall,Cardiff,April 1998
28. C.Y.L. CHEUNG,P. REES and SHORE,K.A., " Gain calculations for unipolar semiconductor lasers ",12th Conference on Semiconductor and Integrated Optoelectronics,(SIOE'98) ,Aberdare Hall,Cardiff,April 1998
29. CHEUNG,C.Y.L., REES,P. and SHORE,K.A.," Estimation of threshold current for unipolar intersubband semiconductor lasers ",Semiconductor Quantum Wells and Dots ,DERA,Malvern , June 1998
30. CHEUNG,C.Y.L., REES, P. and SHORE,K.A.," Modulation bandwidth and gain calculations for near-infra-red Intersubband semiconductor lasers ", IOP Meeting on 'Vertical transport and intersubband processes in low-dimensional structures ',Sheffield,October 1998