P.J.R. Laybourn

Bio: P.J.R. Laybourn is an academic researcher from University of Glasgow. The author has contributed to research in topics: Semiconductor laser theory & Semiconductor ring laser. The author has an hindex of 12, co-authored 21 publications receiving 900 citations.

Operating regimes of GaAs-AlGaAs semiconductor ring lasers: experiment and model

Abstract: Theory and experiments of single-mode ridge waveguide GaAs-AlGaAs semiconductor ring lasers are presented. The lasers are found to operate bidirectionally up to twice the threshold, where unidirectional operation starts. Bidirectional operation reveals that just above threshold, the lasers operate in a regime where the two counterpropagating modes are continuous wave. As the injected current is increased, a new regime appears where the intensities of the two counterpropagating modes undergo alternate sinusoidal oscillations with frequency in the tens of megahertz range. The regime with alternate oscillations was previously observed in ring lasers of the gas and dye type, and it is here reported and investigated in semiconductor ring lasers. A theoretical model based on a mean field approach for the two counterpropagating modes is proposed to study the semiconductor ring laser dynamics. Numerical results are in agreement with the regime sequence experimentally observed when the injected current is increased (i.e., bidirectional continuous-wave, bidirectional with alternate oscillations, unidirectional). The boundaries of the different regimes are studied as a function of the relevant parameters, which turn out to be the pump current and the conservative and dissipative scattering coefficients, responsible for an explicit linear coupling between the two counterpropagating field modes. By a fitting procedure, we obtain good numerical agreement between experiment and theory, and also an estimation for the otherwise unknown scattering parameters.

Unidirectional bistability in semiconductor waveguide ring lasers

Abstract: Large-diameter ridge-guided semiconductor lasers weakly coupled to a straight output waveguide show unidirectional operation and directional bistability at currents up to about twice the threshold. The direction of lasing in the ring may be controlled by biasing contacts at either end of the coupled guide.

Planar optical waveguides formed by silver-ion migration in glass

Abstract: A detailed study has been carried out on the propagation-mode characteristics of graded-index planar optical waveguides formed by silver-sodium ion exchange. It has been found that the index profile can be accurately modeled by a monotonic decrease from a maximum value at the surface, following a second-order polynomial distribution. Definition of an effective diffusion constant leads to a universal mode-dispersion diagram applicable over a wide range of fabrication conditions. Interferometric observations of the refractive-index profile, together with electron microprobe analysis, give further support to the second-order polynomial distribution. The index profile has also been compared with silver-concentration profiles predicted by interdiffusion theory. Results obtained are also relevant to methods of coupling between planar and circular fiber-optical waveguides, where sections of optical fiber undergo ion exchange.

Alternate oscillations in semiconductor ring lasers

Abstract: We report on fabrication and characterization of single-longitudinal- and transverse-mode semiconductor ring lasers. A bifurcation from bidirectional stable operation to a regime with alternate oscillations of the counterpropagating modes was observed experimentally and is theoretically explained through a two-mode model. Analytical expressions for the onset and the frequency of the oscillations are derived, and L I curves numerically evaluated. Good quantitative agreement between theory and measurements made over a large number of tested devices is obtained. © 2002 Optical Society of America OCIS codes: 140.3560, 230.3120, 190.3100.

Fabrication of ion-exchanged optical waveguides from dilute silver nitrate melts

Abstract: Optical waveguides have been fabricated from silver nitrate melts diluted with sodium nitrate. Several important advantages are gained, including control over the surface refractive index value. On the basis of regular solution theory, the relationship between the surface index and the melt dilution is determined. Modification of the index profile with dilution, as predicted by interdiffusion theory, is discussed and the self-diffusion constant of silver ions in a typical soda-lime glass is measured.

Silicon-based optoelectronics

Abstract: The decade of the 1990's is an opportune time for scientists and engineers to create cost-effective silicon "superchips" that merge silicon photonics with advanced silicon electronics on a silicon substrate. We can expect significant electrooptical devices from Column IV materials (Si, Ge, C and Sn) for a host of applications. The best devices will use strained-layer epitaxy, doped heterostructures, and bandgap engineering of quantum-confined structures. This paper reviews Si-based photonic components and optoelectronic integration techniques, both hybrid and monolithic. >

Sensitivity of grating couplers as integrated-optical chemical sensors

Abstract: Grating couplers on planar waveguides can be used as integrated-optical sensors responding to (1) changes in the refractive index of a liquid sample covering the waveguide (differential refractometer) and (2) the adsorption and desorption, respectively, of molecules out of a gaseous or liquid sample on the waveguide (gas or chemical sensor). A theory of the sensor sensitivities is developed; conditions for the waveguide parameters in order to obtain high sensitivities are derived. It is shown that effects (1) and (2) can be distinguished by measurements of the effective index changes of both the TE0 and the TM0 modes. In the analysis both nonporous and microporous waveguiding films are considered.

Ion-exchanged glass waveguides: a review

Abstract: Passive glass waveguides made by ion-exchange technique are potential candidates for integrated optics (IO) applications. The authors review the advantages in the technology as applied to fabrication of useful single-mode structures. Progress in process, fabrication, modeling, and waveguide performance using different monovalent cation systems and glass compositions is described with emphasis on fiber-compatible single-mode structures prepared from molten baths. It is shown how a systematic study allows a correlation between the process parameters and the waveguide characteristics so desirable in assuring reproducible characteristics of the devices. >

Electrically pumped InP-based microdisk lasers integrated with a nanophotonic silicon-on-insulator waveguide circuit.

Abstract: A compact, electrically driven light source integrated on silicon is a key component for large-scale integration of electronic and photonic integrated circuits. Here we demonstrate electrically injected continuous-wave lasing in InP-based microdisk lasers coupled to a sub-micron silicon wire waveguide, fabricated through heterogeneous integration of InP on silicon-on-insulator (SOI). The InP-based microdisk has a diameter of 7.5 mum and a thickness of 1 mum. A tunnel junction was incorporated to efficiently contact the p-side of the pn-junction. The laser emits at 1.6 mum, with a threshold current as low as 0.5 mA under continuous-wave operation at room temperature, and a threshold voltage of 1.65 V. The SOI-coupled laser slope efficiency was estimated to be 30 muW/mA, with a maximum unidirectional output power of 10 muW.

III‐V/silicon photonics for on‐chip and intra‐chip optical interconnects

Abstract: In this paper III-V on silicon-on-insulator (SOI) het- erogeneous integration is reviewed for the realization of near infrared light sources on a silicon waveguide platform, suitable for inter-chip and intra-chip optical interconnects. Two bonding technologies are used to realize the III-V/SOI integration: one based on molecular wafer bonding and the other based on DVS- BCB adhesive wafer bonding. The realization of micro-disk lasers, Fabry-Perot lasers, DFB lasers, DBR lasers and mode- locked lasers on the III-V/SOI material platform is discussed. Artist impression of a multi-wavelength laser based on micro- disk cavities realized on a III-V/SOI heterogeneous platform and a microscope image of a realized structure.