Wavelength-tunable organic semiconductor lasers based on elastic distributed feedback gratings

Wavelength-tunable organic semiconductor lasers based on mechanically stretchable polydimethylsiloxane (PDMS) gratings were developed. The intrinsic stretchability of PDMS was explored to modulate the period of the distributed feedback gratings for fine tuning the lasing wavelength. Notably, elastic lasers based on three typical light-emitting molecules show com-parable lasing threshold values analogous to rigid devices and a continuous wavelength tunability of about 10 nm by mechanic-al stretching. In addition, the stretchability provides a simple solution for dynamically tuning the lasing wavelength in a spec-tral range that is challenging to achieve for inorganic counterparts. Our work has provided a simple and efficient method of fab-ricating tunable organic lasers that depend on stretchable distributed feedback gratings, demonstrating a significant step in the advancement of flexible organic optoelectronic devices.

Critical dispersion of chirped fiber Bragg grating for eliminating time delay signature of distributed feedback laser chaos

Optical chaos has attracted widespread attention owing to its complex dynamic behaviors.However,the time delay signature(TDS)caused by the external cavity mode reduces the complexity of optical chaos.We propose and numerically demonstrate the critical dispersion of chirped fiber Bragg grating(CFBG)for eliminating the TDS of laser chaos in this work.The critical dispersion,as a function of relaxation frequency and bandwidth of the optical spectrum,is found through extensive dynamics simulations.It is shown that the TDS can be eliminated when the dispersion of CFBG is above this critical dispersion.In addition,the influence of dispersive feedback light and output light from a laser is investigated.These results provide important quantitative guidance for designing chaotic semiconductor lasers without TDS.

Single-mode GaSb-based laterally coupled distributed-feedback laser for CO_(2)gas detection

We report on a GaSb-based laterally coupled distributed feedback(LC-DFB)laser with Cr gratings operating at 2004 nm for CO_(2)detection application.Butterfly packaged with single-mode fiber pigtailed,the laser diode operates in the continuous-wave mode in a temperature range from-10℃to 60℃,with a maximum output power of 2 mW and a maximum side-mode suppression ratio over 30 dB.Wavelength-modulated absorption spectroscopy of CO_(2)demonstrates the applicability of the LC-DFB laser to tunable diode laser absorption spectroscopy.Furthermore,the diode junction temperature,which is measured by using the wavelength shift method,exhibits a maximum value of 17℃in the single-mode operation range.

Numerical Simulation of External-Cavity Distributed Feedback Semiconductor Laser

We propose a theoretical model to describe external-cavity distributed feedback semiconductor lasers and investigate the impact of the number of external feedback points on linewidth and side-mode suppression ratio through numerical simulation. The simulation results demonstrate that the linewidth of external-cavity semiconductor lasers can be reduced by increasing the external cavity length and feedback ratio, and adding more external feedback points can further narrow the linewidth and enhance the side mode suppression ratio. This research provides insight into the external cavity distributed feedback mechanism and can guide the design of high-performance external cavity semiconductor lasers. .

Investigation of 980nm Ridge Waveguide Lasers with Current Non-Injection Regions by He Ion Implantaion

The technology of He ion implantation for improving the catastrophic optical damage (COD) level of 980nm semiconductor lasers is introduced.After He ion implantation,p-GaAs obtain higher resistivity than before.About 25μm-long current non-injection regions are introduced near both facets,where the injection current is blocked by high resistivity area.The current non-injection regions can reduce carriers inject to facets,and the rate of the non-radiative recombination are reduced.So the COD level is higher than before.The He ion implantation LDs exhibit no COD failure until the rollover occure at a mean maximum power of 440.5mW.Mean COD level of conventional LDs is given as 407.5mW.Compared to conventional LDs,the mean maximum output power level of He ion implantation LDs is improved by 8%.

Effect of DBR Geometry on Reflectivity and Spectral Linewidth of DBR Lasers

The linewidths of InGaAs-GaAs-AlGaAs DBR lasers with varied DBR dimensional parameters are measured and analyzed. These lasers were built with different DBR grating lengths and depths in order to explore the effect of the size of the DBR on its coupling coefficient and reflectivity,and hence on the linewidth of the laser diodes. The linewidths were measured by employing a self heterodyne linewidth measurement system. The experimental and calculated data for DBR reflectivity and spectral linewidth are given. The relationship between these data and the dimensions of the DBR is analyzed. Based on this analysis,the effect of the DBR geometry on the linewidth of the lasers is explored. The results give useful information related to the design and fabrication of such DBR lasers.

Thermal Characterization of 1.3 μm InAsP/InGaAsP Ridge Waveguide MQW Lasers Based on I-V Method

An experimental way for the thermal characterization ofsemiconductor lasers based on I-V method under pulse drivingconditions has been developed, with which the thermal characteristicsof strain compensated 1.3 μm InAsP/InGaAsP ridge waveguide MQW laserchips have been investigated. The results show that, by measuring andanalyzing the I- V characteristics under appropriate pulse drivingconditions at different has sink Temperatures, the thermal resistanceof the laser diodes could be easily deduced. The driving Current andjunction voltage waveforms of the laser ships under different pulsedriving Conditions are also discussed.

A Single Mode980 nm In Ga As/Ga As/Al Ga As Large Optical Cavity Quantum Well Laser with Low Vertical Divergence Angle

To achieve high optical power as well as low vertical divergence angle,a new kind of optim ized large opti- cal cavity (L OC) structure is applied to a ridge waveguide 980 nm In Ga As/ Ga As/ Al Ga As m ulti- quantum well laser.The optical power density in the waveguide is successfully reduced.The maxim um output power is more than 40 0 m W with a slope efficiency of 0 .89W/ A and the far- field vertical divergence angle is lowered to 2 3°.

Tunable Distributed Bragg Reflector Laser Fabricated by Bundle Integrated Guide

The tunable BIG RW distributed Bragg reflector lasers with two different coupling coefficient gratings are proposed and fabricated.The threshold current of the laser is 38mA and the output power is more than 8mW.The tunable range of the laser is 3 2nm and the side mode suppression ratio is more than 30dB.The variation of the output power within the tunable wavelength range is less than 0 3dB.

High Slope Efficiency and High Power 850nm Oxide-Confined Vertical Cavity Surface Emitting Lasers

High slope efficiency and high power selected oxide-confined 850nm VCSELs grown by MOCVD are reported.The slope efficiency and the threshold current respectively are 0 82mW/mA and 2 59mA with a 9μm diameter oxidation aperture at 25℃.The maximum power of 16mW is obtained at 23mA current bias.The minimum threshold current can be as low as 570μA with a 5μm diameter oxidation aperture at 25℃.The maximum saturated power is 5 5mW.

Measurement of Cavity Loss and Quasi-Fermi-Level Separation for Fabry-Pérot Semiconductor Lasers

A fitting process is used to measure the cavity loss and the quasi Fermi level separation for Fabry Pérot semiconductor lasers.From the amplified spontaneous emission (ASE) spectrum,the gain spectrum and single pass ASE obtained by the Cassidy method are applied in the fitting process.For a 1550nm quantum well InGaAsP ridge waveguide laser,the cavity loss of about ～24cm -1 is obtained.

Gain Switch of an AlGaInP Red Light Semiconductor Laser Diode

We solve the single mode coupled rate equations by computer,simulate the behavior of a gain switch of an AlGaInP red light semiconductor laser diode,and find the characteristic of FWHM of pulses changing with the amplitude of modulation signal, the bias current, and the modulated frequency. On this basis, we conduct experiments. The experiment results accord with the simulations well.

Measurement of 3db Bandwidth of Laser Diode Chips

An accurate technique for measuring the frequency response of semiconductor laser diode chips is proposed and experimentally demonstrated.The effects of test jig parasites can be completely removed in the measurement by a new calibration method.In theory,the measuring range of the measurement system is only determined by the measuring range of the instruments network analyzer and photo detector.Diodes' bandwidth of 7 5GHz and 10GHz is measured.The results reveal that the method is feasible and comparing with other method,it is more precise and easier to use.

Parallel generation of low-correlation wideband complex chaotic signals using CW laser and external-cavity laser with self-phase-modulated injection

A novel scheme for generating optical chaos is proposed and experimentally demonstrated,which supports to simultaneously produce two low-correlation chaotic signals with wideband spectrum and suppressed time-delay-signature(TDS).In the proposed scheme,we use the output of an external-cavity semiconductor laser(ECSL)as the driving signal of a phase modulator to modulate the output of a CW laser.Then the phase-modulated continuous-wave(CW)light is split into two parts,one is injected back into the ECSL that outputs one chaotic signal,while the other part is passed through a dispersion module for generating another chaotic signal simultaneously.The experimental results prove that the proposed scheme has three merits.Firstly,it can improve the bandwidth of ECSL-based chaos by several times,and simultaneously generate another wideband flat-spectrum chaotic signal.Secondly,the undesired TDS characteristics of the simultaneously-generated chaotic signals can be efficiently suppressed to an indistinguishable level within a wide parameter range,as such the complexities of the chaotic signals are considerably high.Thirdly,the correlation coefficient between these two simultaneously-generated chaotic signals is smaller than 0.1.The proposed scheme provides an attractive solution for parallel multiple chaos generation,and shows great potential for multiple channel chaos communications and multiple random bit generations.

Chaos generation by a hybrid integrated chaotic semiconductor laser

We design a hybrid integrated chaotic semiconductor laser with short-cavity optical feedback.It can be assembled in a commercial butterfly shell with just three micro-lenses.One of them is coated by a transflective film to provide the optical feedback for chaos generation while insuring regular laser transmission.We prove the feasibility of the chaos generation in this compact structure and provide critical external parameters for the fabrication by theoretical simulations.Rather than the usual changeless internal parameters used in previous simulation research,we extract the real parameters of the chip by experiment.Moreover,the maps of the largest Lyapunov exponent with varying bias current and feedback intensity Kap demonstrate the dynamic characteristics under different external-cavity conditions.Each laser chip has its own optimal external cavity length(L)and feedback intensity(Kap)to generate chaos because of the different internal parameters.We have acquired two ranges of optimal parameters(L=4 mm,0.12〈Kap〈0.2 and L=5 mm,0.07〈Kap〈0.12)for two different chips.

Waveguide external cavity narrow linewidth semiconductor lasers

Narrow linewidth light source is a prerequisite for high-performance coherent optical communication and sensing.Waveguide-based external cavity narrow linewidth semiconductor lasers(WEC-NLSLs)have become a competitive and attractive candidate for many coherent applications due to their small size,volume,low energy consumption,low cost and the ability to integrate with other optical components.In this paper,we present an overview of WEC-NLSLs from their required technologies to the state-of-the-art progress.Moreover,we highlight the common problems occurring to current WEC-NLSLs and show the possible approaches to resolving the issues.Finally,we present the possible development directions for the next phase and hope this review will be beneficial to the advancements of WEC-NLSLs.

High wall-plug efficiency 808-nm laser diodes with a power up to 30.1 W

A very highly efficient InGaAlAs/AlGaAs quantum-well structure was designed for 808 nm emission,and laser diode chips 390-μm-wide aperture and 2-mm-long cavity length were fabricated.Special pretreatment and passivation for the chip facets were performed to achieve improved reliability performance.The laser chips were p-side-down mounted on the AlN submount,and then tested at continuous wave(CW)operation with the heat-sink temperature setting to 25℃using a thermoelectric cooler(TEC).As high as 60.5%of the wall-plug efficiency(WPE)was achieved at the injection current of 11 A.The maximum output power of 30.1 W was obtained at 29.5 A when the TEC temperature was set to 12°C.Accelerated life-time test showed that the laser diodes had lifetimes of over 62111 h operating at rated power of 10 W.

Electrically pumped metallic and plasmonic nanolasers

In recent years, there have been a significant number of demonstrations of small metallic and plasmonic lasers. The vast majority of these demonstrations have been for optically pumped devices. Electrically pumped devices are advantageous for applications and could demonstrate concepts not amenable for optical pumping. However, there have been relatively few demonstrations of electrically pumped small metal cavity lasers. This lack of results is due to the following reasons： there are limited types of electrically pumped gain media available; there is a significantly greater level of complexity required in the fabrication of electrically pumped devices; finally, the required components for electrical pumping restrict cavity design options and furthermore make it intrinsically more difficult to achieve lasing. This review looks at the motivation for electrically pumped nanolasers, the key issues that need addressing for them to be realized, the results that have been achieved so far including devices where lasing has not been achieved, and potential new directions that could be pursued.

Research on quantum well intermixing of 680 nm AlGaInP/GaInP semiconductor lasers induced by composited Si-Si_(3)N_(4) dielectric layer

The optical catastrophic damage that usually occurs at the cavity surface of semiconductor lasers has become the main bottleneck affecting the improvement of laser output power and long-term reliability.To improve the output power of 680 nm AlGaInP/GaInP quantum well red semiconductor lasers,Si-Si_(3)N_(4)composited dielectric layers are used to induce its quantum wells to be intermixed at the cavity surface to make a non-absorption window.Si with a thickness of 100 nm and Si_(3)N_(4)with a thickness of 100 nm were grown on the surface of the epitaxial wafer by magnetron sputtering and PECVD as diffusion source and driving source,respectively.Compared with traditional Si impurity induced quantum well intermixing,this paper realizes the blue shift of 54.8 nm in the nonabsorbent window region at a lower annealing temperature of 600 ℃ and annealing time of 10 min.Under this annealing condition,the wavelength of the gain luminescence region basically does not shift to short wavelength,and the surface morphology of the whole epitaxial wafer remains fine after annealing.The application of this process condition can reduce the difficulty of production and save cost,which provides an effective method for upcoming fabrication.

Tunable and broadband microwave frequency combs based on a semiconductor laser with incoherent optical feedback

Based on a semiconductor laser （SL） with incoherent optical feedback, a novel all-optical scheme for generating tunable and broadband microwave frequency combs （MFCs） is proposed and investigated numerically. The results show that, under suitable operation parameters, the SL with incoherent optical feedback can be driven to operate at a regular pulsing state, and the generated MFCs have bandwidths broader than 40 GHz within a 10 dB amplitude variation. For a fixed bias current, the line spacing （or repetition frequency） of the MFCs can be easily tuned by varying the feedback delay time and the feedback strength, and the tuning range of the line spacing increases with the increase in the bias current. The linewidth of the MFCs is sensitive to the variation of the feedback delay time and the feedback strength, and a linewidth of tens of KHz can be achieved through finely adjusting the feedback delay time and the feedback strength. In addition, mappings of amplitude variation, repetition frequency, and linewidth of MFCs in the parameter space of the feedback delay time and the feedback strength are presented.