External-cavity Quantum-dot Laser Research Articles

Sideband amplitude modulation absorption spectroscopy of CH4 at 1170 nm.

We report on the method of the sideband amplitude modulation (SAM) to achieve high-sensitivity spectroscopy with a fiber electro-optic modulator (fiber-EOM). This method increases the signal to noise ratio (SNR) by a factor of forty, comparing with conventional absorption spectroscopy. It is a temporal balanced detection to eliminate the intensity noise of the light source, and capable of preserving an undistorted Doppler profile for further quantitative analysis. Taking advantage of the newly developed fiber-EOM, SAM is applicable for various spectroscopies with a simple experimental setup. We performed SAM on CH43ν3 overtone band at 1170 nm using an external cavity Quantum dot laser. We demonstrated that one of the absorption lines buried in the other ten times stronger nearby lines was clearly extracted. SAM shows great potential on the molecular spectroscopy, where the spectrum is complicated and quantitative analysis is required.

Influence of Antireflection Coating on the Performance of Broadly Tunable Quantum Dot External Cavity Laser

Influence of Antireflection Coating on the Performance of Broadly Tunable Quantum Dot External Cavity Laser

A review of external cavity-coupled quantum dot lasers

Since the external cavity quantum dot laser was first demonstrated, the performances have been improved in terms of operation temperature, output power, pulse generator and tuneability based on the naturally size fluctuation of quantum dot. Nowadays, the external cavity quantum dot sources have been successfully used in different absorption spectroscope techniques, in industry, biomedical and research. In this paper we reviewed the recent developments of quantum dot lasers operated in a grating-coupled external cavity system where a single frequency and wide tunable wavelength range were easily obtained by adjusting the grating angle. In all cases, we mainly stressed the significant progresses in understanding of basic optical and electronic properties to enable the importance steps forward. The prospects for further progress directed towards stability, mode-hoping-free tuning range, miniaturization and integration of the external cavity quantum dot lasers also reviewed.

A mode-locked external-cavity quantum-dot laser with a variable repetition rate

A mode-locked external-cavity laser emitting at 1.17-μm wavelength using an InAs/GaAs quantum-dot gain medium and a discrete semiconductor saturable absorber mirror is demonstrated. By changing the external-cavity length, repetition rates of 854, 912, and 969 MHz are achieved respectively. The narrowest −3-dB radio-frequency linewidth obtained is 38 kHz, indicating that the laser is under stable mode-locking operation.

A grating-coupled external cavity InAs/InP quantum dot laser with 85-nm tuning range

The optical performance of a grating-coupled external cavity laser based on InAs/InP quantum dots is investigated. Continuous tuning from 1391 nm to 1468 nm is realized at an injection current of 1900 mA. With the injection current increasing to 2300 mA, the tuning is blue shifted to some extent to the range from 1383 nm to 1461 nm. By combining the effect of the injection current with the grating tuning, the total tuning bandwidth of the external cavity quantum-dot laser can reach up to 85 nm. The dependence of the threshold current on the tuning wavelength is also presented.

Compact Dual-Wavelength InAs/GaAs Quantum-Dot External-Cavity Laser Stabilized by a Single Volume Bragg Grating

Stable dual-wavelength operation has been achieved by combining a single volume Bragg grating with a quantum-dot-based gain medium in a compact external cavity configuration, with extreme ease of alignment. The dual-wavelength output was centered at 1179.9 and 1182.8 nm, with each mode exhibiting a spectral bandwidth 0.2 nm. A maximum output power of 186 mW was achieved, with both modes displaying a sidemode suppression-ratio (SMSR) of over 34 dB. Furthermore, the SMSR remained well over 26 dB within a broad current range (350-1000 mA) and temperature range (10.5 C-40 °C). Unlike previous dual-wavelength configurations that used quantum-well-based devices, the quantum-dot-based laser here presented displays improved stability and resilience to changes in operating temperature and current.

Quantum dot lasers grown by gas source molecular-beam epitaxy

We report on the InAs quantum dot lasers grown by gas source molecular-beam epitaxy, respectively, on GaAs and InP substrates. Room temperature continuous-wave operation was achieved for both InAs/GaAs and InAs/InP quantum dot lasers, respectively, at 1.10μm and 1.54–1.70μm wavelength region. More than 50mW optical power was collected from one facet of the InAs/GaAs quantum dot lasers at 20°C, while for InAs/InP quantum dot lasers the maximum output power was measured as 30mW. For InAs/InP material system, by increasing the layer thickness of deposited InAs from 3.0 to 3.5 monolayers, the lasing wavelength can be extended from 1.5–1.6μm to 1.6–1.7μm. Moreover, a tunable quantum dot external cavity laser was demonstrated, utilizing the broad gain profile of InAs quantum dots.

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.

A narrow-line-width external cavity quantum dot laser for high-resolution spectroscopy in the near-infrared and yellow spectral ranges

We demonstrate a diode laser system which is suitable for high-resolution spectroscopy in the 1.2 μm and yellow spectral ranges. It is based on a two-facet quantum dot chip in a Littrow-type external cavity configuration. The laser is tunable in the range 1125–1280 nm, with an output power of more than 200 mW, and exhibits a free-running line width of 200 kHz. Amplitude and frequency noise were characterized, including the dependence of the frequency noise on the cavity length. Frequency stabilization to a high-finesse reference cavity is demonstrated, whereby the line width was reduced to approx. 30 kHz. Using a femtosecond frequency comb, the residual frequency instability was determined and found to be below 300 Hz on the time scales 1–300 s. Yellow light (>3 mW) at 578 nm was generated by frequency doubling in an enhancement cavity containing a PPLN crystal. The source has potential application for precision spectroscopy of ultra-cold Yb atoms and cold molecular hydrogen ions.

External-cavity quantum-dot laser tunable through 1.55μm

The optical performance of external-cavity lasers based on InAs∕InGaAsP quantum dot laser diodes is investigated. The broad electroluminescence reveals a gain spectrum with full width at half maximum of at least 175nm. By fabricating as-cleaved ridge lasers of different length and width, tuning ranges as high as 110nm have been achieved at wavelengths encompassing 1.55μm. The tuning ranges and efficiencies obtained are limited by internal losses and competition between the external-cavity lasing modes and the laser diode natural lasing modes. The laser diode length is found to affect both the wavelength tuning range and the threshold current density, which is consistent with a quantum-dot type density of states.

Low-threshold quantum dot lasers with 201 nm tuning range

A grating-coupled external-cavity quantum dot laser is tuned across a 201 nm range at a maximum bias of 2.87 kA/cm/sup 2/. One order of magnitude less than the bias required for comparable tuning of quantum well lasers. The tuning range increases for higher cavity losses of the quantum dot laser.