DFB Laser Research Articles

Tbps parallel random number generation based on a single quarter-wavelength-shifted DFB laser

We propose and experimentally demonstrate a parallel physical random number generator (Ph-RNG) based on a single quarter-wavelength-shifted distributed feedback laser (QWS-DFB LD). Though simply connecting the two output ports of the QWS-DFB LD to form a cross-coupled perturbation, we simultaneously produce two paths of complex optical chaotic signals with a bandwidth above 10 GHz. Furthermore, a dual-channel Ph-RNG with a bit rate of order terabit per second (Tbps) is implemented by combining a multi-bit extraction method. Final results show that our generated physical random numbers can successfully pass standard benchmark tests for randomness.

Monolithic Integrated Linear Frequency Modulated Dual-Wavelength DFB Laser Chip with High Linearity and Its Application in Long Distance Ranging

Monolithic Integrated Linear Frequency Modulated Dual-Wavelength DFB Laser Chip with High Linearity and Its Application in Long Distance Ranging

Ultralow-threshold quasi-CW lasing from FAPbBr3 perovskite first-order DFB laser

Metal halide perovskites are emerging materials for integrated photonics. Here we report a quasi-CW pumped ultra-low ASE/lasing threshold formamidinium lead bromide (FAPbBr3) laser. The laser achieved stable lasing at 555 nm with a full width at half maximum (FWHM) of 0.6 nm, showing a low lasing threshold of 22.6 μJ cm−2 under 3.5 nanosecond quasi-CW excitation at room temperature. The material also showed an ultra-low ASE threshold of 46 μJ cm−2 under the same pumping condition. Through polymer doping, we showed that the material’s performance can be improved by increasing bimolecular recombination rate with reduced grain size.

Thermal Characterisation of Hybrid, Flip-Chip InP-Si DFB Lasers

WA detailed thermal analysis of a hybrid, flip-chip InP-Si DFB laser is presented in this work. The lasers were experimentally tested at different operating temperatures, which allowed for deriving their thermal performance characteristics: the temperature dependence of threshold current, lasing slope, and output spectrum. Using these data, the laser thermal resistance was calculated (Rth = 75.9 K/W), which allows for predicting the laser temperature during operation. This metric is also used to validate the thermal finite element models of the laser. A sensitivity study of the laser temperature was performed using these models, and multiple routes for minimising both the laser thermal resistance and thermal coupling to the carrier die are presented. The most effective way of decreasing the laser temperature is the direct attachment of a heat sink on the laser top surface.

10 kW peak power, single-frequency 1553 nm nanosecond pulsed fiber laser for time-of-flight LIDAR

A 10 kW peak power, 10 ns duration and 6 kHz repetition rate fiber laser system at 1553 nm based on an Er/Yb co-doped large-mode-area fiber, is demonstrated experimentally. The seed laser is provided by a DFB laser switched with a semiconductor optical amplifier. Its optical spectrum, linewidth, and beam quality are measured and discussed. This pulsed laser with short pulse duration and high peak power could be a candidate for the laser source of time-of-flight light detection and ranging (LIDAR).

Small-form-factor Gaussian-modulated coherent-state transmitter for CV-QKD using a gain-switched DFB laser.

We report a directly modulated distributed feedback laser operating in gain-switching mode for preparing the coherent states required for the Gaussian-modulated coherent-state (GMCS) continuous-variable quantum key distribution (CV-QKD) protocol. The proposed single-component quantum transmitter design eliminates the need for external modulators, decreasing the complexity of GMCS CV-QKD systems. The experimental results demonstrate a potential asymptotic secret key rate value of 2.63 Mbps over an 11-km fiber link, making the directly modulated GMCS transmitter particularly suitable for metropolitan optical networks where compactness, robustness, and low cost are key desirable features.

Extremely Efficient DFB Lasers with Flat-Top Intra-Cavity Power Distribution in Highly Erbium-Doped Fibers.

High-performance erbium-doped DFB fiber lasers are presently required for several sensing applications, whilst the current efficiency record is only a few percent. Additionally, a flat-top intra-cavity power distribution that is not provided in traditional DFB lasers is preferred. Moreover, cavity lengths of <20 cm are attractive for fabrication and packaging. These goals can be achieved using highly erbium-doped fiber (i.e., 110 dB/m absorption at 1530 nm), providing high gain with proper engineering of coupling coefficients. In this paper, for a given background fiber loss, first the optimum intra-cavity signal powers for various pump powers are numerically calculated. Then, for a fully unidirectional laser, optimum coupling profiles are determined. Design diagrams, including contour maps for optimum cavity lengths, maximum output powers, maximum intra-cavity signal powers, and quality factors considering various pump powers and background fiber losses, are presented. The laser pump and intra-cavity signal distribution are also calculated for a realistic, feasible modified coupling profile considering a strong unidirectionality. The DFB laser is finally simulated using generalized coupled-mode equations for such modified profiles. The efficiency of more than 22% can be realized, which is the highest reported for DFB lasers based only on erbium-doped fiber.

1.3‑μm High‐Speed Directly‑Modulated InGaAlAs/InP DFB Laser with Integrated DBR Feedback Region

1.3‑μm High‐Speed Directly‑Modulated InGaAlAs/InP DFB Laser with Integrated DBR Feedback Region

High Spatial Resolution TGD‑OFDR Based on Internally Modulated DFB Laser

High Spatial Resolution TGD‑OFDR Based on Internally Modulated DFB Laser

Nonlinear Frequency Correction Technology of DFB laser with High Frequency Modulation for FMCW LiDAR

Nonlinear Frequency Correction Technology of DFB laser with High Frequency Modulation for FMCW LiDAR

Nonlinear Dynamics and Potential Application of a DFB Laser Subject to Dual-Beam Injection

This paper presents a detailed experimental investigation of the nonlinear dynamics of a dual-beam optically injected semiconductor laser. Unlike previous works, we focus on the situation where the power and the frequency of the injection light wave are fixed and the free running frequency of the laser subject to optical injection is in between the two injection beams that have a large frequency separation. The nonlinear dynamics of the slave laser (SL), i.e., the laser subject to optical injection, for different SL forward bias currents are examined. Results show, in addition to the regenerated injection light wave, a fundamental oscillation together with its harmonics are generated when the SL is interacted with its nearby injection beam. The SL output frequency components are stabilised when one of the harmonics of the fundamental oscillation is located at the injection beam that is far away from the free running SL. More than six-fold improvement in the frequency stability of the resultant output microwave signal, compared to that generated by optical mixing, is obtained. Experimental results also show the SL nonlinear dynamics have different behaviours when the two injection beams have different frequency separations.

Directly modulated 25 Gbaud/s tunable in-series DFB laser array for WDM systems

Directly modulated 25 Gbaud/s tunable in-series DFB laser array for WDM systems

Dual-wavelength DFB Laser Array Based on Sidewall Grating and Lateral Modulation of the Grating Coupling Coefficient

A monolithic dual-wavelength DFB laser array based on sidewall gratings and a novel modulation of the grating coupling coefficient is proposed and demonstrated experimentally. The grating coupling coefficient distribution along the cavity is modulated by changing the alignment between the gratings on the two sidewalls. The frequency difference between the two lasing modes can be modulated by changing the cavity length and grating recess depth. A series of microwave signals in the range of 50 GHz to 59 GHz is observed after beating the two optical lines in a photodetector. The measured optical linewidths are 250 kHz and 850 kHz when the cavity length is 1200 μm and 1000 μm, respectively.

2.7 μm GaSb-based distributed feedback lasers with laterally coupled gratings

We report on a high-performance GaSb-based quantum well laterally coupled distributed feedback laser emitting at wavelength of 2.7 μm. The first-order grating structure of chromium(Cr) is designed to obtain the maximum coupling coefficient, and is defined alongside the ridge waveguide by electron beam lithography. The DFB laser emits an output power of 4.3 mW in a single-mode operation at a heat-sink temperature of 20 °C. Continuous wavelength tuning has been obtained by varying the injection current at a tuning rate of 0.012 nm mA−1. The mixmum side mode suppression ratio is as high as 54.9 dB, which is the highest value ever reported at the wavelength region of 2.7 μm. In addition, the loss margin introduced by Cr gratings is estimated to be 5.02

Open-path anti-pollution multi-pass cell-based TDLAS sensor for the online measurement of atmospheric H2O and CO2 fluxes.

We report an open-path and anti-pollution multi-pass cell based tunable diode laser absorption spectroscopy (TDLAS) sensor, which was designed for online measurement of atmospheric H2O and CO2 fluxes. It is mainly composed of two plano-convex mirrors coated on a convex surface, which makes it different from traditional multi-pass cells. This design does not allow a direct contact between the coating layer of the lens and air, thereby realizing the anti-pollution effect of the coating layer. Two DFB lasers operating at 1392 nm and 2004 nm were employed to target H2O and CO2 absorption lines, respectively. Allan analysis of variance indicated that detection limits of H2O and CO2 were 5.98 ppm and 0.68 ppm, respectively, at an average time of 0.1 s. The sensor performance was demonstrated by measuring CO2 and H2O flux emissions at Jiangdu Agricultural Monitoring Station in Jiangsu Province. The results were compared with those obtained using the commercial instrument LI-7500, which is based on non-dispersive infrared technology. The developed gas analysis instrument exhibited good consistency with commercial instruments, and its accuracy was comparable; thus, it has strong application prospects for flux measurements in any ecosystem.

High-power distributed feedback lasers with high-order surface curved gratings.

A novel, to the best of our knowledge, broad-area distributed feedback laser with high-order surface curved gratings has been fabricated based on standard near ultraviolet lithography. The characteristics of increasing output power and mode selection are achieved simultaneously by using a broad-area ridge as well as an unstable cavity structure composed of curved gratings and a high-reflectivity coated rear facet. Suppression of high-order lateral modes is realized by setting current injection/non-injection regions and asymmetric waveguides. This DFB laser emitting around 1070 nm has achieved a spectral width of 0.138 nm and a maximum output power of 915 mW kink-free optical power. The threshold current and side-mode suppression ratio of the device are 370 mA and 33 dB, respectively. The simple manufacturing process and stable performance give this high-power laser broad application prospects in the fields of light detection and ranging, laser pumps, optical disk access, etc.

Photonically Generated Frequency Hopped Linear Frequency Modulated Signal Using a DFB Laser

Threats and security are critical issues in a multi-RADAR environment, which severely affect the performance metrics of a RADAR system, such as range resolution, false detection, and image quality. In a multi-RADAR environment, the issues of jamming, spoofing, and interferences should be considered for practical implementation. In this paper, we experimentally demonstrate a photonically generated frequency hopped linear frequency modulated (Ph-FHLFM) signal using injection locking in a DFB laser. For a proof of concept, we develop Ph-FHLFM with an eight-step and four-step hopping, each step having a bandwidth of 2 GHz and 1 GHz, respectively, and a total bandwidth of 8 GHz. The generated Ph-FHLFM signal detects two objects separated by 10, 5, and 2.5 cm with a maximum error of 3 mm. Further, for the proof of concept of the interference agility of the Ph-FHLFM signal, target objects are detected in the presence of an interferer, which is a conventional linear frequency modulated radar with the same/different bandwidths and chirps. Unlike in conventional LFM, the Ph-FHLFM signal overcomes the false detection and maintains a similar resolution in both scenarios, with and without an interferer.

(Digital Presentation) Correlative Evaluation Between Water Concentration and Voltage Fluctuation of PEFC Under Low-Humidity and Load-Change Operations Based on Laser Spectroscopy

Low-humidity and load-change operations of polymer electrolyte fuel cells (PEFCs) often tend to induce the excessive voltage drop called “undershoot”. Especially when the load current rapidly increases in steps, the strong electro-osmotic drag dehydrates the electrolyte membrane and deteriorates the proton conductivity, resulting in a temporal increase in ohmic loss. To identify a factor for causing undershoot, it is necessary to precisely grasp the transient water behavior within PEFCs operated under load-change conditions. In the previous works, several researchers vigorously explored the water vapor distribution along flow fields of working cells with micro gas chromatography (μGC) [1]. Although GC techniques provide more accurate species concentrations, it takes a long time (at least two minutes) to collect a gas sample and identify a species. As an alternative approach, the authors have developed a single-ended fiber-optic sensor to measure the in-situ concentration of water vapor within narrow channels of fuel cells at high speed and with high accuracy based on tunable diode laser absorption spectroscopy (TDLAS) [2]. TDLAS is one of the high-speed and high-sensitive absorption spectroscopy techniques which detect the absorbance of a chemical species and identify its concentration using infrared diode laser. This study became able to monitor the transient variation of water vapor concentration in the anode channel of a PEFC during low-humidity and load-change operations using the TDLAS-based fiber-optic sensor and discussed the correlation between the water behavior and the voltage fluctuation. Furthermore, the effects of load current and compression pressure were also investigated.Figs. 1(a) and 1(b) show the dynamic responses of cell voltage and the transient water concentrations in the anode channel of the operating PEFC assembled under two different compression pressures of 1.0 and 2.0 MPa. The electrode area of the experimental cell is 50 mm2. Two separators on both sides have a single-straight channel (1.0 mm width, 1.0 mm depth, 6.0 mm length). Hydrogen (stoichiometry: 2.3@1.0A/cm2, 30%RH) and oxygen (stoichiometry: 9.1@1.0A/cm2, 30%RH) were fed to the anode and cathode channel in the co-flow arrangement. The fiber-optic probe for water detection was positioned at the fractional location of x/L=0.5 on the anode side and the modulated beam emitted from a DFB laser diode (wavelength: 1392.5 nm) was directly injected into the channel. The cell temperature is 70oC. The repetitive current cycling was performed between 0.2 A/cm2 for 23 s and 0.6 A/cm2 for 23 s. In the case of the compression pressure of 1.0 MPa, when the current density increases steeply from 0.2 to 0.6 A/cm2, the strong electro-osmotic drag temporarily reduces the water content on the anode side of the electrolyte membrane and increases the ohmic loss, resulting in the voltage undershoot. After a step increase in the current density, the temporal drop of water vapor concentration in the anode channel can also be observed. When the compression pressure is increased to 2.0 MPa, the porosities of the diffusion media are reduced and the water concentration becomes high especially under the anode rib. Thus, even if the current density is increased stepwise after the repeated current cycles, the water shortage in the anode and the undershoot are not caused. It was noted that the strong compression effectively improves the water retaining on the anode side under low-humidity operations and alleviate the voltage undershoot.

Combo-PON OLT Transceiver Using Photonic Integration Technology

In this work, a prototype of 10G Combo-PON OLT transceiver based on photonic integrated circuits (PIC) is proposed and demonstrated. Key optical components for Combo-PON OLT transceiver, including high-power DFB laser, micro-ring modulator and WDM, have been developed and validated. The Combo-PON OLT transceiver integrated four XGS-PON/GPON ports and all ports comply with I-TUT G.984.2 Class C+ standard. The advantages and disadvantages of PIC in PON application are analyzed. The analysis shows that PIC can also provide a cost and power-efficient way to implement the next generation PON transceiver for high density PON ports.

TD-DFT and optical properties of 9,9-dioctyl-9Hfluorene-based oligomer in a thin film and design of DFB laser using ellipsometry studies

TD-DFT and optical properties of 9,9-dioctyl-9Hfluorene-based oligomer in a thin film and design of DFB laser using ellipsometry studies