The detection and measurement of gas concentrations using the characteristic optical absorption of the gas species is important for both understanding and monitoring a variety of phenomena from industrial processes to environmental change. This study reviews the field, covering several individual gas detection techniques including non-dispersive infrared, spectrophotometry, tunable diode laser spectroscopy and photoacoustic spectroscopy. We present the basis for each technique, recent developments in methods and performance limitations. The technology available to support this field, in terms of key components such as light sources and gas cells, has advanced rapidly in recent years and we discuss these new developments. Finally, we present a performance comparison of different techniques, taking data reported over the preceding decade, and draw conclusions from this benchmarking.

/pdf/optical-gas-sensing-a-review-4uaf589xiq.pdf

Optical gas sensing: a review

Semiconductor lasers are convenient and compact sources of light, offering highly efficient operation, direct electrical control and integration opportunities. In this review we describe how semiconductor quantum-dot structures can provide an efficient means of amplifying and generating ultrafast (of the order of 100 fs), high-power and low-noise optical pulses, with the potential to boost the repetition rate of the pulses to beyond 1 THz. Such device designs are opening up new possibilities in ultrafast science and technology.

Mode-locked quantum-dot lasers

This paper summarizes recent advances on InAs/InP quantum dash (QD) materials for lasers and amplifiers, and QD device performance with particular interest in optical communication. We investigate both InAs/InP dashes in a barrier and dashes in a well (DWELL) heterostructures operating at 1.5 mum. These two types of QDs can provide high gain and low losses. Continuous-wave (CW) room-temperature lasing operation on ground state of cavity length as short as 200 mum has been achieved, demonstrating the high modal gain of the active core. A threshold current density as low as 110 A/cm2 per QD layer has been obtained for infinite-length DWELL laser. An optimized DWELL structure allows achieving of a T0 larger than 100 K for broad-area (BA) lasers, and of 80 K for single-transverse-mode lasers in the temperature range between 25degC and 85degC. Buried ridge stripe (BRS)-type single-mode distributed feedback (DFB) lasers are also demonstrated for the first time, exhibiting a side-mode suppression ratio (SMSR) as high as 45 dB. Such DFB lasers allow the first floor-free 10-Gb/s direct modulation for back-to-back and transmission over 16-km standard optical fiber. In addition, novel results are given on gain, noise, and four-wave mixing of QD-based semiconductor optical amplifiers. Furthermore, we demonstrate that QD Fabry-Perot (FP) lasers, owing to the small confinement factor and the three-dimensional (3-D) quantification of electronic energy levels, exhibit a beating linewidth as narrow as 15 kHz. Such an extremely narrow linewidth, compared to their QW or bulk counterparts, leads to the excellent phase noise and time-jitter characteristics when QD lasers are actively mode-locked. These advances constitute a new step toward the application of QD lasers and amplifiers to the field of optical fiber communications

/pdf/recent-advances-on-inas-inp-quantum-dash-based-semiconductor-1due9iu1dr.pdf

Recent Advances on InAs/InP Quantum Dash Based Semiconductor Lasers and Optical Amplifiers Operating at 1.55 $\mu$ m

https://www.ulp.ethz.ch/content/dam/ethz/special-interest/phys/quantum-electronics/ultrafast-laser-physics-dam/publications_awards/publications/2006/248__PhysRep_429__67__2006_.pdf

Passively modelocked surface-emitting semiconductor lasers

This paper presents a selection of recent advances on two-section passively mode-locked InGaAs-based quantum-dot laser diodes. Pulse generation is demonstrated for repetition rates ranging from 310 MHz to 240 GHz, and with pulse durations ranging from the picosecond to the sub-400 fs regime. Mode-locking trends in these devices are discussed, and device performance improvements in terms of pulse duration, output power, and noise properties are presented. Design rules for reducing the pulse duration, increasing the output power, and improving noise performance are outlined. Implementation of tapered waveguide structures yields significant performance improvements, allowing the simultaneous achievement of ultrashort, Fourier-limited pulse generation with low amplitude noise, low timing jitter, and narrow RF linewidths.

InGaAs Quantum-Dot Mode-Locked Laser Diodes

We demonstrate mode locking in a two-section quantum-dot laser that produces output powers up to 45 mW at 1260 nm. The pulse duration could be varied from 2 ps to as short as 400 fs at the 21 GHz pulse repetition rate.

High-power picosecond and femtosecond pulse generation from a two-section mode-locked quantum-dot laser

Positive and negative output power, spectral and current-voltage characteristics of the In(Ga)As and InAs(Sb) based heterostructure light-emitting diodes with the episide-down' construction grown onto heavily doped n + -InAs have been examined in the 20-200°C temperature range. Optically pumped LEDs composed from the above heterostructures or from InSb exhibited output characteristics fairly close to the conventional LEDs. Wavelength and temperature variation of the emission power in the 3.3-8 μm spectral range was compared with the phenomenological model based on the expectations of the negative luminescence power (NLP) and saturation current (I sat ). The crossover of forward bias power at 1 A and negative power at I = I sat takes place at 90 and 160°C for 5.3 and 4.3 μm LEDs correspondingly.

Towards efficient mid-IR LED operation: optical pumping, extraction or injection of carriers?

The emission of episide down bonded InAsSbP/In(Ga)As/n+-InAs and graded InAsSb(P) light-emitting diodes (LEDs) with λmax = 3.3–5.5 μm has been modified with an 'internal' Fabry–Perot cavity or bandpass filter attached to the LED with an optical glue. Positive and negative emission with the full width at half-maximum close to that of the filter (8–20 meV) have been obtained in the 20–50 °C temperature range.

InAs and InAsSb LEDs with built-in cavities

InAsSbP/InAs0.9Sb0.1/InAs DH photodiodes (λ0.1 = 5.2 μm, 300 K) operating in the 77–353 К temperature range

Ultrashort pulses of 1.7 ps at frequency as low as 9.7 GHz are demonstrated by passive mode-locking of monolithic two-section InAs/InGaAs (/spl lambda/=1.28 /spl mu/m) quantum-dot laser. Pulse shortening with the absorber section bias increase is observed.

N. D. Il’inskaya

Papers

High-power picosecond and femtosecond pulse generation from a two-section mode-locked quantum-dot laser

Towards efficient mid-IR LED operation: optical pumping, extraction or injection of carriers?

InAs and InAsSb LEDs with built-in cavities

InAsSbP/InAs0.9Sb0.1/InAs DH photodiodes (λ0.1 = 5.2 μm, 300 K) operating in the 77–353 К temperature range

Mode-locking at 9.7 GHz repetition rate with 1.7 ps pulse duration in two-section QD lasers