Broadly tunable high-power InAs/GaAs quantum-dot external cavity diode lasers

A record broadly tunable high-power external cavity InAs/GaAs quantum-dot diode laser with a tuning range of 202 nm (1122 nm-1324 nm) is demonstrated. A maximum output power of 480 mW and a side-mode suppression ratio greater than 45 dB are achieved in the central part of the tuning range. We exploit a number of strategies for enhancing the tuning range of external cavity quantum-dot lasers. Different waveguide designs, laser configurations and operation conditions (pump current and temperature) are investigated for optimization of output power and tunability. (C) 2010 Optical Society of America

Photonic processing for wideband cancellation and spectral discrimination of RF signals

Photonic signal processing is used to implement common mode signal cancellation across a very wide bandwidth utilising phase modulation of radio frequency (RF) signals onto a narrow linewidth laser carrier. RF spectra were observed using narrow-band, tunable optical filtering using a scanning Fabry Perot etalon. Thus functions conventionally performed using digital signal processing techniques in the electronic domain have been replaced by analog techniques in the photonic domain. This technique was able to observe simultaneous cancellation of signals across a bandwidth of 1400 MHz, limited only by the free spectral range of the etalon. © 2013 David M. Benton.

Self-mode-locked quantum-dot vertical-external-cavity surface-emitting laser

We present the first self-mode-locked optically pumped quantum-dot semiconductor disk laser. Our mode-locked device emits sub-picosecond pulses at a wavelength of 1040 nm and features a record peak power of 460 W at a repetition rate of 1.5 GHz. In this work, we also investigate the temperature dependence of the pulse duration as well as the time-bandwidth product for stable mode locking. © 2014 Optical Society of America.

High-power quantum-dot vertical-external-cavity surface-emitting laser exceeding 8 W

We report on a record-high output power from an optically pumped quantum-dot vertical-external-cavity surface-emitting laser, optimized for high-power emission at 1040 nm. A maximum continuous-wave output power of 8.41 W is obtained at a heat sink temperature of 1.5 °C. By inserting a birefringent filter inside the laser cavity, a wavelength tuning over a range of 45 nm is achieved. © 2014 IEEE.

Numerical modeling of fiber lasers with long and ultra-long ring cavity

We highlight two important aspects related to a mathematical modeling of pulsed fiber lasers with long and ultra-long ring cavity -impact of an initial noise and a cavity length on generation of single optical pulses. Using as an example a simple scalar model of a ring fiber laser that describes the radiation build-up from noise and the following intra-cavity pulse dynamics during a round trip we study dependence of generated pulse characteristics on the resonator length in the range from 30 m up to 2 km. © 2013 Optical Society of America.

Study of EEPN mitigation using modified RF pilot and Viterbi-Viterbi based phase noise compensation

We propose - as a modification of the optical (RF) pilot scheme -a balanced phase modulation between two polarizations of the optical signal in order to generate correlated equalization enhanced phase noise (EEPN) contributions in the two polarizations. The method is applicable for n-level PSK system. The EEPN can be compensated, the carrier phase extracted and the nPSK signal regenerated by complex conjugation and multiplication in the receiver. The method is tested by system simulations in a single channel QPSK system at 56 Gb/s system rate. It is found that the conjugation and multiplication scheme in the Rx can mitigate the EEPN to within 1/2 orders of magnitude. Results are compared to using the Viterbi-Viterbi algorithm to mitigate the EEPN. The latter method improves the sensitivity more than two orders of magnitude. Important novel insight into the statistical properties of EEPN is identified and discussed in the paper. © 2013 Optical Society of America.

Pulse shaping in mode-locked fiber lasers by in-cavity spectral filter

We numerically show the possibility of pulse shaping in a passively mode-locked fiber laser by inclusion of a spectral filter into the laser cavity. Depending on the amplitude transfer function of the filter, we are able to achieve various regimes of advanced temporal waveform generation, including ones featuring bright and dark parabolic-, flat-top-, triangular- and saw-tooth-profiled pulses. The results demonstrate the strong potential of an in-cavity spectral pulse shaper for controlling the dynamics of mode-locked fiber lasers. © 2014 Optical Society of America.

Biochemical sensor based on a novel all-fibre cavity ring down spectroscopy technique incorporating a tilted fibre Bragg grating

A novel all-fibre cavity ring down spectroscopy technique is demonstrated where a tilted fibre Bragg grating in the cavity provides sensitivity to surrounding refractive index. A decay time of 450ns was attained when sensing water.

112Gbit/s RF assisted dual-carrier DP-16-QAM in installed and new build WDM applications

The performance of a 112Gbit/s dual-carrier DP-16-QAM channel in various WDM configurations is characterized. Variations of the dispersion map, ROADM count and system length are experimentally evaluated and compared with numerical simulation. © 2012 OSA.

Novel resonant cavity TDM demodulation scheme for FBG sensing

A novel time-division-multiplexed Bragg grating interrogation system is presented, utilising a semiconductor optical amplifier within a resonating cavity. Without fast electronics, closely spaced low reflectivity gratings are interrogated with high signal power and low noise.

Tailored waveform generation in mode-locked fiber lasers by in-cavity pulse shaper

We numerically show the possibility of pulse shaping in a mode-locked fiber laser by inclusion of an amplitude-phase spectral filter into the laser cavity. Various advanced temporal waveforms are generated, including parabolic, flat-top and triangular pulses. © 2014 OSA.

Resonant cavity time-division-multiplexed fiber Bragg grating sensor interrogator

The first resonant-cavity time-division-multiplexed (TDM) fiber Bragg grating sensor interrogation system is reported. This novel design uses a pulsed semiconductor optical amplifier in a cyclic manner to function as the optical source, amplifier, and modulator. Compatible with a range of standard wavelength detection techniques, this optically gated TDM system allows interrogation of low reflectivity "commodity" sensors spaced just 2 m apart, using a single active component. Results demonstrate an exceptional optical signal-to-noise ratio of 36 dB, a peak signal power of over +7 dBm, and no measurable crosstalk between sensors. Temperature tuning shows that the system is fully stable with a highly linear response. © 2004 IEEE.

In-cavity transformations for new nonlinear regimes of pulse generation in mode-locked fibre lasers

We review recent progress in the research on nonlinear mechanisms of pulse generation in passively mode-locked fibre lasers. These include parabolic self-similar pulse mode-locking, a mode-locking regime featuring pulses with a triangular distribution of the intensity, and spectral compression arising from nonlinear pulse propagation. We also report on the possibility of achieving various regimes of advanced temporal waveform generation in a mode-locked fibre laser by inclusion of a spectral filter into the laser cavity.

Recent advances in the field of vertical-external-cavity surface-emitting lasers

Vertical-external-cavity surface-emitting lasers (VECSELs) have proved to be versatile lasers which allow for various emission schemes which on the one hand include remarkably high-power multi-mode or single-frequency continuouswave operation, and on the other hand two-color as well as mode-locked emission. Particularly, the combination of semiconductor gain medium and external cavity provides a unique access to high-brightness output, a high beam quality and wavelength flexibility. Moreover, the exploitation of intra-cavity frequency conversion further extends the achievable radiation wavelength, spanning a spectral range from the UV to the THz. In this work, recent advances in the field of VECSELs are summarized and the demonstration of self-mode-locking (SML) VECSELs with sub-ps pulses is highlighted. Thereby, we present studies which were not only performed for a quantum-well-based VECSEL, but also for a quantum-dot VECSEL.