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

The optical performance of a grating-coupled external Continuous tuning from 1391 nm to 1468 nm is realized at cavity laser based on InAs/InP quantum dots is investigated. 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.     

A Linearly-Polarized Cesium Vapor Laser with Fundamental Mode Output and Low Threshold

We report a cesium vapor laser with fundamental mode output and a wavelength of 894 nm. The laser is pumped by a laser diode array with an external cavity of a holographic grating by using Littrow＇s structure. A slope efbciency of 22.4% is obtained by using a pumping source with a linewidth of 0.26 nm and 80 kPa methane as the buffer gas. The threshold pumping power is 1.56 W.     

High-sensitivity long-period fiber grating sensor with SAN/cryptophane A for coal mine gas detection

A high-sensitivity long-period fiber grating （LPFG） methane sensor that contains a compact and uniform styrene-acrylonitrile （SAN）/cryptophane A nanofilm is presented. The sensor is prepared by using an automatic dip-coater in a solution of cryptophane A, SAN resin dissolved in ortho-dichlorobenzene, a low- volatile solvent. The effect of film thickness on the LPFG＇s resonant wavelength is thoroughly investigated. The optimum sensor among the three LPFGs with different film thicknesses is directly used to detect the methane concentration in a coal mine gas sample. The results indicate that the sensors with film thicknesses of 484 to 564 nm exhibit a redshifted resonant wavelength when the methane concentration is increased from 0% to 3.5% （vol）. The data demonstrates that the sensor with a film thickness of 484 nm has remarkable sensitivity （~0.633 nm%-X）, and its detection limit can reach 0.2%. The methane concentrations determined by our sensor are consistent with those obtained by gas chromatography.     

Gain Measurement and Anomalous Decrease of Peak Gain at Long Wavelength for InAs/GaAs Quantum-Dot Lasers

Mode gain spectrum is measured by the Fourier series expansion method for InAs/GaAs quantum-dot （QD） lasers with seven stacks of QDs at different injection currents. Gain spectra with distinctive peaks are observed at the short and long wavelengths of about 1210nm and 1300nm. For a QD laser with the cavity length of 1060μm, the peak gain of the long wavelength first increases slowly or even decreases with the injection current as the peak gain of the short wavelength increases quickly, and finally increases quickly before approaching the saturated values as the injection current further increases.     

Frequency stabilization of diode laser to 1.637 μm based on the methane absorption line

The frequency of an external-cavity diode laser has been stabilized to 1.637 μm by using the reference of absorption lines of methane. The method can be applied to wavelength division multiplexed optical communication, fiber-optic sensing systems, as well as the high-sensitivity detection of methane. The derivative-like error signal yielded by frequency modulation and phase sensitivity detection technology is inputted into the PI feedback loop circuit in order to stabilize the frequency to the line center. After stabilization, the frequency fluctuation of diode laser is held within 5.6 MHz, and the root of Allan variance of error signal reaches a minimum of 1.66×10-10 for an average time of 10 s.     

All solid-state, injection-seeded Tirsapphire ring laser

In this letter, we present an all solid-state, injection-seeded Ti:sapphire laser. The laser is pumped by a laser diode pumped frequency-doubled Nd:YAG laser, and injection-seeded by an external cavity laser diode with the wavelength between 770 and 780 nm. The single longitude mode and the doubling efficiency of the laser are obtained after injection seeding. The experimental setup and relative results are reported. It is a good candidate laser source for mobile differential absorption lidar (DIAL) system.     

All solid-state, injection-seeded Ti: sapphire ring laser

In this letter, we present an all solid-state, injection-seeded Ti:sapphire laser. The laser is pumped by a laser diode pumped frequency-doubled Nd:YAG laser, and injection-seeded by an external cavity laser diode with the wavelength between 770 and 780 nm. The single longitude mode and the doubling efficiency of the laser are obtained after injection seeding. The experimental setup and relative results are reported.It is a good candidate laser source for mobile differential absorption lidar (DIAL) system.     

All solid-state passively Q-switched frequency-doubled intra-cavity Nd:GdVO_4/KTP laser

In this letter, we present an all solid-state, injection-seeded Ti:sapphire laser. The laser is pumped by a laser diode pumped frequency-doubled Nd:YAG laser, and injection-seeded by an external cavity laser diode with the wavelength between 770 and 780 nm. The single longitude mode and the doubling efficiency of the laser are obtained after injection seeding. The experimental setup and relative results are reported. It is a good candidate laser source for mobile differential absorption lidar (DIAL) system.     

Continuous-wave operation of InAs/InP quantum dot tunable external-cavity laser grown by metal-organic chemical vapor deposition

We demonstrate high-performance broadband tunable external-cavity lasers(ECLs) with the metal-organic chemical vapor deposition(MOCVD) grown In As/In P quantum dots(QDs) structures. Without cavity facet coatings, the 3-d B spectral bandwidth of the Fabry–Perot(FP) laser is approximately 10.8 nm, while the tuning bandwidth of ECLs is 45 nm.Combined with the anti-reflection(AR)/high-reflection(HR) facet coating, a 92 nm bandwidth tuning range has been obtained with the wavelength covering from 1414 nm to 1506 nm. In most of the tuning range, the threshold current density is lower than 1.5 k A/cm2. The maximum output power of 6.5 m W was achieved under a 500 m A injection current.All achievements mentioned above were obtained under continuous-wave(CW) mode at room temperature(RT).     

Output Characteristics of an InP/InGaAsP Triangle Microcavity Laser

Mode competitions between modes with different output coupling efficiencies can result in optical bistability under certain asymmetric nonlinear gain. For a GaInAsP/InP equilateral triangle microlaser with the side length of 10μm, the drop of the output power with the increase of the injection current is observed corresponding to transverse mode transitions. Furthermore, the measured laser spectra up to 270K show that lasing modes coexist with the wavelength interval of 39nm at 240K. The emission at 5.2THz can be expected by the mode frequency beating with the 39nm interval.     

Distributed Bragg reflector laser(1.8 μm) with 10 nm wavelength tuning range

We report a 1.8 μm two-section distributed Bragg reflector laser using butt-jointed In Ga As P bulk material as the waveguide core layer. The threshold current is 17 m A and the output power is 8 m W on average. The threshold current, output power, and emitting wavelength dependences on temperature are measured. The obtained wavelength tuning range is 10 nm. This device has potential applications in simultaneous multiple-gas detection.     

A broadband external cavity tunable InAs/GaAs quantum dot laser by utilizing only the ground state emission

A broadband external cavity tunable laser is realized by using a broad-emitting spectral InAs/GaAs quantum dot (QD) gain device. A tuning range of 69 nm with a central wavelength of 1056 nm, is achieved at a bias of 1.25 kA/cm2 only by utilizing the light emission from the ground state of QDs. This large tunable range only covers the QD ground-state emission and is related to the inhomogeneous size distribution of QDs. No excited state contributes to the tuning bandwidth. The application of the QD gain device to the external cavity tunable laser shows its immense potential in broadening the tuning bandwidth. By the external cavity feedback, the threshold current density can be reduced remarkably compared with the free-running QD gain device.     

Experimental study of actively mode-locked semiconductor laser with grating external cavity

In this paper,complete mode-locking optical pulses have been obtained froman actively mode-locked GaAs/GaAlAs semiconductor laser with grating external cavity.Theshortest optical pulse is 7.3 ps measured by second harmonic generation(SHG)autocorrelator.The repetition rate is 995.12 MHz and the central wavelength is 798.4 nm.The effect ofmodulation frequency,modulation current,and bias current on the optical pulses width areinvestigated.     

Stable multi-wavelength thulium-doped fiber laser based on all-fiber Mach–Zehnder interferometer

We propose and experimentally demonstrate a multi-wavelength thulium-doped fiber（TDF） laser based on all-fiber Mach–Zehnder interferometer（MZI） at 1.9 mm. Here a segment of 4 m single-mode TDF is pumped by 1568 nm fiber laser for 2 mm band optical gain. The MZI includes two cascaded 3 d B coupler. A segment of 3.5 m long un-pumped polarization-maintaining TDF and polarization controller（PC） are joined in the ring cavity to suppress the mode competition. Multi-wavelength lasers at 1.9 mm with wavelength number from one to four are obtained by adjusting the PC and the stability of output power of multi-wavelength fiber laser is analyzed.     

Efficient femtosecond optical parametric oscillator pumped by all solid-state mode-locking Yb:YCOB laser

We experimentally demonstrate a femtosecond optical parametric oscillator(OPO) synchronously pumped by a home-made solid-state mode-locking Yb:YCOB laser, which is capable of laser pulse as short as 102 fs and average power of 620 m W at the central wavelength of 1052 nm. By using a periodically poled lithium niobate with tuning of the grating periods from 28.5 to 31.5 μm as the nonlinear gain crystal, tunable femtosecond pulses from 1444 to 1683 nm are realized by conveniently adjusting the OPO cavity length with 76.8 MHz repetition rate. The maximum average output power is 152 m W at 1568 nm, corresponding to an idler power of 75 m W at 3197 nm as well as 36.6% total extraction efficiency.     

Double-Arched LD Array Stagger Pumped Electro-Optic Q-Switched Nd：YAG Laser without Water Cooling

We report an experimental study on a double-arched LD array stagger pumped electro-optic Q-switched Nd：YAG laser without water cooling by using a convex-concave compensate resonator. Perfect matching of the gain field inside the rod and the fundamental mode of the cavity is made by this structure. When the repetition rate is 20 Hz, A maximum output energy at 1064 nm wavelength of 176 mJ （M2=1.55） and 9.6 ns FWHM pulse width in fundamental mode Q-switch operation is obtained with LD injection current 120 A. The optical-optical conversion efficiency is 14.7%, the divergence angle of the output beam is about 1.8 mrad.     

High sensitivity refractive index gas sensing enhanced by surface plasmon resonance with nano-cavity antenna array

The surface plasmon resonance gas sensor is presented for refractive index detection using nano-cavity antenna array.The gas sensor monitors the changes of the refractive index by measuring the spectral shift of the resonance dip,for modulating the wavelength of incident light.It is demonstrated that minute changes in the refractive index of a medium close to the surface of a metal film,owing to a shift in the resonance dip of the wavelength,can be detected.The average detection sensitivity is about 3200 nm/RIU(refractive index units),which is more than twice that of a metal grating-based gas sensor.The reflectivity of the surface plasmon resonance dip is only ～ 0.03%,and the full widths at half maximum(FWHMs) of bandwidth of the angle and wavelength are ～ 0.20° and 4.71nm,respectively.     

A compact graphene Q-switched erbium-doped fiber laser using optical circulator and tunable fiber Bragg grating

We demonstrate a passively Q-switched tunable erbium-doped fiber laser(EDFL)based on graphene as a saturable absorber(SA).A three-port optical circulator(OC)and a strain-induced tunable fiber Bragg grating(TFBG)are used as the two end mirrors in an all-fiber linear cavity.The Q-switched EDFL has a low pump threshold of 23.8 mW.The pulse repetition rate of the fiber laser can be widely changed from 9.3 kHz to 69.7 kHz by increasing the pump power from23.8 mW to 219.9 mW.The minimum pulse duration is 1.7μs and the highest pulse energy is 25.4 nJ.The emission wavelength of the laser can be tuned from 1560.43 nm to 1566.27 nm by changing the central wavelength of the straininduced TFBG.     

Continuous-Wave Operation of GaN Based Multi-Quantum-Well Laser Diode at Room Temperature

Room-temperature operation of cw GaN based multi-quantum-well laser diodes （LDs） is demonstrated. The LD structure is grown on a sapphire （0001） substrate by metalorganic chemical vapour deposition. A 2.5μm × 800μm ridge waveguide structure is fabricated. The electrical and optical characteristics of the laser diode under direct current injection at room temperature are investigated. The threshold current and voltage of the LD under cw operation are 110mA and 10.5V, respectively. Thermal induced series resistance decrease and emission wavelength red-shift are observed as the injection current is increased. The full width at half maximum for the parallel and perpendicular far field pattern （FFP） are 12° and 32°, respectively.     

Tunable Diode Laser Absorption Spectroscopy Detection of N2O at 2.1μm Using Antimonide Laser and InGaAs Photodiode

Tunable diode laser absorption spectroscopy detection of N2 0 around 2.1 μm is demonstrated by using a homemade InGaAsSb/AlGaAsSb MQW laser diode and an InGaAs wavelength extended photodiode. Details of the devices and the detection system are described. In the system, the laser is driven by low frequency pulses with long duration to form a wavelength scan around 4741 cm^-1; the absorption information is obtained from the detected signal of the photodiode. By using a gas cell with 15cm path length, a detection limit is estimated to be smaller than 0.2 Torr.