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We discuss the design, modelling, fabrication and characterisation of an integrated tuneable birefringent waveguide for quantum cascade lasers. We have fabricated quantum cascade lasers operating at wavelengths around 4450 nm that include polarisation mode converters and a differential phase shift section. We employed below laser threshold electroluminescence to investigate the single pass operation of the integrated device. We use a theory based on the electro-optic properties of birefringence in quantum cascade laser waveguides combined with a Jones matrix based description to gain an understanding of the electroluminescence results. With the quantum cascade lasers operating above threshold we demonstrated polarisation control of the output. © 2013 Optical Society of America.

We discuss the design, fabrication and characterization of waveguide polarization mode converters for quantum cascade lasers operating at 4.6 µm. We have fabricated a quantum cascade laser with integrated polarization mode converter that emits light of 69% Transverse Electrical (TE) polarization from one facet and 100% Transverse Magnetic (TM) polarization from the other facet. © 2012 Optical Society of America.

The design, fabrication and characterization of a monolithic double-ring quantum- cascade laser (DRQCL) are described. At a wavelength of 4.6m, we demonstrate tunable, single-mode operation of a DRQCL and use it as a source for spectroscopy of CO gas.

By integrating a polarization mode converter we have obtained significant amounts of Transverse Electrical light from a quantum cascade laser. First results indicate up to around 18%TE light in an elliptically polarized output.

We report the development of room-temperature distributed-feedback quantum-cascade lasers operating in a single mode in the 3.34 to 3.35 μm wavelength range. First-order lateral gratings with high aspect ratio (the ratio between the grating etch depth and its period) were formed using inductively coupled plasma etching. The as-cleaved lasers emit in pulsed regime with a sidemode suppression ratio of up to 24 dB and a peak single-mode output power of 130 mW from a single facet.

We present a low-phase noise microwave oscillator based on a version of an optical fiber optoelectronic oscillator that employs self-injection of a resonant tunneling diode oscillator, integrated with a photo-detector, that drives a laser diode. ©2010 IEEE.

We report on the design, fabrication, and characterization of a unidirectional quantum cascade ring laser operating at a wavelength of around 3.4 µm at 200 K. A unidirectional operation is achieved by incorporating an "S-shaped" crossover waveguide in a manner that it couples light from the counterclockwise direction to the preferred clockwise direction. The ring laser unidirectionality is confirmed by measuring the counterpropagating wave suppression ratio (CWSR) as a function of injection current. At 1.5 times the threshold current, the CWSR is 9 that is 90% of the light is emitted in the favored (clockwise) direction. © 2010 American Institute of Physics.

Discrete-mode quantum-cascade lasers have been developed in the InGaAsAlAsSbInP materials system. For an uncoated 10-µm-wide ridge waveguide and 3000-µm-long cavity, the laser had a threshold current density J th of 4.2 kA·cm2 {Ith}=1.5 A)at 300 K with a slope efficiency of 80 mW/A. A stable single-mode emission near 3.3 µm with a sidemode suppression ratio of nearly 25 dB was observed and a tuning coefficient of 0.22 nm/K was obtained in the temperature range of 253 K < T <303 K. © 2006 IEEE.

We present a review of Resonant Tunneling Diode (RTD) OptoElectronic Integrated Circuits (OEICs). Resonant tunneling diodes (RTDs) can be relatively easily integrated on the same chip as optoelectronic components and in this paper we discuss the integration of RTDs with laser diodes, electroabsorption modulators and photodiodes. The RTD provides the OEIC with negative differential resistance over a wide bandwidth. RTDs are highly nonlinear devices and by applying nonlinear dynamics we have recently gained considerable insight into the operation of the RTD OEICS and that has allowed us to design, fabricate and characterize OEICs for wireless/photonic interfaces. © 2010 Copyright SPIE - The International Society for Optical Engineering.

We report on optical injection-locking of a microwave-photonic oscillator based on the integration of a resonant tunneling diode optical waveguide photodetector with a communication laser diode. The oscillator locking was achieved with in-fiber optical powers as low as 0.2 mW, and locking ranges up to 23.8 MHz for in-fiber optical power of few milliwatts and with phase-noise suppression below -110 dBc/Hz at 10-kHz frequency offset from the center frequency. The circuit's dynamics are well described as an optically controlled Linard oscillator. © 2006 IEEE.

We report experimental and numerical results on frequency locking, quasi-periodic and chaotic outputs induced by wireless signals on a nonlinear photonics interface consisting of a laser diode driven by a resonant tunnelling diode.

A new way of generating electrical and optical chaotic carriers is demonstrated using an optoelectronic voltage controlled oscillator consisting of a laser diode (LD) driven by a resonant tunneling diode (RTD) perturbed by radio-frequency signals. The high-dimensional broadband (gigahertz-wide) chaotic current produced by the RTD modulates a LD, providing a simple way to convert electrical chaotic signals into optical subcarriers that can be transmitted by conventional optical channels. Since the chaotic current and the chaotic optical subcarriers are controlled accurately and reproducibly by the RTD, we anticipate this concept can be used as the core of a compact, simple, and low-power consumption optical chaos generator for optical communications. © 2009 IEEE.

Recent work on an OptoElectronic Integrated Circuit (OEIC), the resonant tunneling diode-laser diode (RTD-LD) has shown that it can act as an optoelectronic voltage controlled oscillator (OVCO). The RTD-LD oscillates because of the negative differential resistance of the RTD and simply providing the RTD-LD with a dc voltage will cause it to oscillate at frequencies determined by both the external components of the circuit and the value of the dc voltage. It has been observed to oscillate at frequencies as high as 2.2GHz and be tunable from 1.8-2.2GHz as the dc voltage is tuned by 0.5V. Both monolithic and hybrid (separate RTD and LD chips) have been investigated. The hybrid RTD-LD has been accurately modeled as a Liénard's oscillator - closely related to the Van der Pol oscillator. The model is a classic of nonlinear systems theory and explains all of the observed operating features that include synchronization and chaotic output. Applications include wireless to optical signal conversion where phase synchronization has been demonstrated to transfer phase modulated signals from the wireless to the optical domain by modulating the RTD-LD OVCO to produce a phase modulated optical sub-carrier. © 2009 SPIE.

We report on a wireless to optical interface consisting of a laser diode driven by resonant tunneling diode. Circuit electrical behavior and laser output are well predicted by a Liénard's driven oscillator model. ©2008 IEEE.

We report optical experimental frequency division and chaos results in a resonant tunneling diode laser diode driver configuration that forms a self-oscillating circuit. Circuit behavior and laser output results are well predicted using Liénad's equation. © 2008 Optical Society of America.

We report on a hybrid optoelectronic integrated circuit based on a resonant tunnelling diode driving an optical communications laser diode. This circuit can act as a voltage controlled oscillator with optical and electrical outputs. We show that the oscillator operation can be described by Liénard's equation, a second order nonlinear differential equation, which is a generalization of the Van der Pol equation. This treatment gives considerable insight into the potential of a monolithic version of the circuit for optical communication functions including clock recovery and chaotic source applications. © 2008 IEEE.

A hybrid optoelectronic integrated circuit comprising a laser diode driven by a resonant tunnelling diode can output various optical and electrical signal patterns that include self-sustained oscillations, subharmonic and harmonic locking and unlocked signals, with potential applications in optical communication systems. © 2008 The Institution of Engineering and Technology.