Laser Diode Chip Research Articles

A low-magnetic packaging for a distributed Bragg reflector laser diode chip for atomic sensor applications

We implement a distributed Bragg reflector (DBR) laser diode (LD) package with low-magnetic field generation. The package consists of a commercial 795 nm DBR LD chip, a thermo-electric cooler (TEC), a thermistor, a flexible printed circuit board (FPCB) which cancels the magnetic field emitted by the TEC current flow, and a non-magnetic aluminum case. We confirm that the magnetic dipole moment of our low-magnetic package body is about three orders of magnitude smaller than that of a commercial DBR laser package. Moreover, it is shown that our compensating FPCB, the effectiveness of which is supported by computer simulations, reduces the magnetic field magnitude by a factor of 2.2. The FPCB also reduces the magnetic field gradient emitted by the TEC current flow so that gradient-induced spin relaxations are suppressed in applications. A portable optically pumped atomic magnetometer (OPAM) utilizing two low-magnetic packages as light sources is reported as an application of the package and shows a 0.30 pT/Hz1/2 level magnetic sensitivity at a 69 μT external magnetic field; in contrast, the OPAM utilizing the commercial packages showed a magnetic sensitivity of 0.87 pT/Hz1/2.

Laser diode-pumped compact hybrid lithium niobate microring laser.

We demonstrate a compact hybrid lithium niobate microring laser by butt coupling a commercial 980-nm pump laser diode chip with a high-quality Er3+-doped lithium niobate microring chip. Single-mode lasing emission at 1531-nm wavelength from the Er3+-doped lithium niobate microring can be observed with the integrated 980-nm laser pumping. The compact hybrid lithium niobate microring laser occupies the chip size of 3 mm × 4 mm × 0.5 mm. The threshold pumping laser power is 6 mW and the threshold current is 0.5 A (operating voltage 1.64 V) at atmospheric temperature. The spectrum featuring single-mode lasing with small linewidth of 0.05 nm is observed. This work explores a robust hybrid lithium niobate microring laser source which has potential applications in coherent optical communication and precision metrology.

Phase composition design of high performance Al2O3-YAG: Ce ceramic phosphors for high-power laser lighting

The combination of laser diode (LD) chip and Al2O3-YAG: Ce composite ceramic phosphor is considered as one of the best solutions for high-power laser lighting. However, in previous studies on Al2O3-YAG: Ce composite ceramics, the effects of large-scale compositional changes on their luminous properties were rarely noticed, which hinders the understanding of the relationship between ceramic phase composition and the comprehensive properties of white LDs. In this paper, we prepared Al2O3-YAG: Ce composite ceramic phosphors with Ce3+ and Al2O3 concentrations varying widely in the range of 0.5–5 at% and 0–90 at%, respectively. An impurity phase was found in samples with high Ce3+-Al2O3 concentration by SEM images and verified to be CeAl11O18 by XRD patterns. Under high power density laser (2.3–10 W/mm2) excitation, the Ce3+ concentrations corresponding to the highest luminous efficiency of the ceramic increase from 0.5 at% to 3 at% with the introduction of Al2O3. The temperature quenching effect of ceramics is also alleviated. The CRI of ceramics first decreases and then increases with the increase of Al2O3 concentration, and the CRI of 90 at% Al2O3 samples is the highest (75.9). The results show that the introduction of Al2O3 can improve the performance of ceramics from all aspects as long as the optimal composition of Al2O3- YAG: Ce composite ceramics is selected.

Optical transmitter module with hybrid integration of DFB laser diode and proton-exchanged LiNbO3 modulator chip

In this work, a hybrid integrated optical transmitter module was designed and fabricated. A proton-exchanged Mach–Zehnder lithium niobate (LiNbO3) modulator chip was chosen to enhance the output extinction ratio. A fiber was used to adjust the rotation of the polarization direction caused by the optical isolator. The whole optical path structure, including the laser chip, lens, fiber, and modulator chip, was simulated to achieve high optical output efficiency. After a series of process improvements, a module with an output extinction ratio of 34 dB and a bandwidth of 20.5 GHz (from 2 GHz) was obtained. The optical output efficiency of the whole module reached approximately 21%. The link performance of the module was also measured.

COMPARATIVE EVALUATION OF EFFICACY OF SCALING AND ROOT PLANING WITH AND WITHOUT CHLORHEXIDINE CHIP AND DIODE LASER IN CHRONIC PERIODONTITIS PATIENTS

Introduction: The motive of the present study is to comparatively measure the competence and effectiveness of diode laser and chlorhexidine chip as adjuncts to the scaling and root planing procedure, in patients with chronic periodontitis.
 Aim: To evaluate the efficacy of diode laser and chlorhexidine chip before and after scaling and root planing in the management of chronic periodontitis. The objective is to compare the efficacy of chlorhexidine chip and diode laser before and after scaling and root planning on clinical parameters.
 Study and design: Randomized clinical trial with split mouth design done in the Department of Periodontics and Implantology.
 Materials and methods: Twenty chronic periodontitis patients having a probing pocket depth of 5mm-7mm on at least one interproximal site in each quadrant of the mouth were selected in the study. After initial treatment, four sites in each patient were randomly subjected to scaling and root planing (control), chlorhexidine chip application (CHX chip group), diode laser (810 nm) decontamination (Diode laser group) or combination of both (Diode laser and chip group). All subjects received a clinical periodontal examination by single examiner who recorded all the variables by manual procedure. Clinical parameters namely Plaque index (PI), Gingival Index (GI), probing pocket depth (PPD) and clinical attachment level (CAL) were assessed at baseline, one month and three months. Results were statistically analysed using one-way ANOVA followed by Post Hoc Analysis.
 Results: The differences in PPD reduction and CAL gain between control group and CHX chip and combination groups were statistically significant (p<0.05) at three months, whereas, the diode laser group did not show any significant difference from the control group.
 Conclusion: Within the limitations in the present study, the following conclusions were derived, i.e., chlorhexidine local delivery alone or in combination with diode laser decontamination is effective in improving oral hygiene, reducing gingival inflammation, reducing probing pocket depth and improving clinical attachment levels when used as adjuncts to scaling and root planing in non-surgical periodontal therapy of patients with chronic periodontitis.
 Keywords: Diode laser decontamination, Local drug delivery, Scaling and root planing.

MEMS-VCSEL as a tunable light source for OCT imaging of long working distance

We present a wavelength tunable vertical-cavity surface-emitting laser (VCSEL) constructed by die-bonding a half-cavity InGaAs laser diode (LD) chip onto a silicon-on-insulator chip with a microelectromechanical system electrostatic diaphragm mirror that functions as a Fabry–Perot interferometer. As a result of the short cavity length, the integrated tunable LD has single-mode lasing characteristics with an extremely large coherence length of 150 m or more. The developed wavelength tunable LD is used to perform swept-source optical coherence tomography with a large scan depth, which is applicable to ophthalmic observation for the diagnosis of pathologic nearsightedness based on the measurement of the axial length of an eye.

Experimental investigation of the package of diode laser chip based on lateral heat flow suppression

To improve slow axis beam quality of diode laser (LD) and decrease slow axis divergence angle, a new package with lateral heat flow suppression was designed utilizing the difference in thermal conductivity between air and heat sink. The finite element analysis software was used to analyze the temperature distribution with lateral flow suppression package. It is shown that diode laser chip soldered on trough heat sink with width W=120 μm and length L=4000 μm can reduce slow axis divergence angle about 14%, from 12.25° to 10.49°, when working current was 15A. Correspondingly, beam parameter product (BPP) can reduce from 5.344 mm·mrad to 4.5763 mm·mrad and the brightness of slow axis increased about 5.5% than before. According to the result, the lateral flow suppression package can weaken higher order mode caused by thermal lens effect of diode laser so that decrease slow axis divergence angle effectively.

82‐1: Invited Paper: Latest Status of Blue and Green Laser Diodes and Laser Packages for Display Applications

The wall‐plug efficiency of blue and green Laser Diode (LD) chips for laser display applications exceeding 48% and 21% respectively was achieved. Our development laser package with 24 blue LD chips installed has achieved an optical output power over 120 watts.

Design and evaluation of optical laser diodes LD positioning arrangement and multiple input/ multiple output MIMO-OFDM systems

Optical communication system for the next generation of wireless communication systems are an exciting, unparalleled new technology. This paper presents a new visible light positioning algorithm system based on position by utilized neural network, which depending on directly measured received signal strength (RSS) information of 3D coordinates. This algorithm is called light positioning algorithm neural network (LPANN) which used 5 laser diodes LDs, each one consists of 5×5 LD chips. In addition, a novel multi Input multiple output (MIMO) orthogonal frequency division multiplexing (OFDM) based VLC systems generalized laser diodes (LD) modulation scheme as second part of this paper that is called Zero Forcing Equalizer Neural network ZFENN algorithm which based on 4 × 4 optical MIMO-VLC. It is accomplished by using LD index modulation and spatial multiplexing. Actual and imaginary parts of the complex time domain OFDM signals are therefore separated first and then, bipolar signals are transmitted through VLC channels by encoding sign-information in LD indexes. In addition, a novel receiver configuration is also suggested for flat frequency or limited channel scenarios. Based on the results of this analysis, the positioning accuracy have been improved, so this is lead to enhance data rate. While, by using the second part of the MIMO-OFDM system that leads to enhancing the SNR and BER more than 10-4, which are introduced to eliminate multi-user interference (MUI).

Design and microfabrication strategies for thin-film, flexible optical neural implant.

Advanced polymer science and design technologies are constantly evolving to meet ever-growing expectations for flexible optical MEMS. In this work, we present design and microfabrication considerations for designed flexible Polymeric Opto-Electro-Mechanical Systems (POEMS). The presented methods integrate waveguide fabrication and laser diode (LD) chip assembly with Lawrence Livermore National Laboratory's (LLNL's) flexible thin-film technology to enable LLNL's first neural optoelectrode that can deliver guided light for neural activation. We support our findings with electrical and optical bench verification tests, present thermal simulation models to analyze heat dissipation of laser light sources on polymer substrates and discuss potential modifications for next generation prototypes. This fully integrated approach will allow spatial precision, scalability and more particularly, longer lifetime, needed to enable chronic studies of brain activities.

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 sub-mount, and then tested at continuous wave (CW) operation with the heat-sink temperature setting to 25 °C 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 62 111 h operating at rated power of 10 W.

Wavelength-stabilized DBR high-power diode laser

This paper reports a wavelength-stabilized high-power diode laser emitting up to 14 W CW in the 9xx nm range. Wavelength stabilization is achieved by a distributed Bragg reflector (DBR) monolithically integrated in the diode laser chip. Key features are identical layer epitaxy (ILE) and the use of a multiple-order electron beam lithography (EBL) optical confining grating. ILE avoids any regrowth or complex technology processes, while EBL multiple-order grating allows narrow-band back reflection and effective lateral optical confinement, and makes it possible to stabilize multiple wavelengths on the same wafer using a manufacturable and reliable technology. DBR diode lasers with different pitches, whose wavelengths were 3 nm spaced, were fabricated and high spectral purity (95% optical power within about 0.6 nm) and wavelength stability were measured. Moreover, the high uniformity of performances across the wafer with different emitted wavelengths demonstrates the maturity of the proposed technology for high-yield, high-volume laser diode production for wavelength-stabilized applications. A multi-emitter module, including ten DBR diode lasers, collimating and focusing optics, showed 100 W CW wavelength-stabilized output power at 14 A in a 135 μm core optical fiber within 0.17 NA. Single diode lasers, or multi-emitter modules, can be used to combine high-power optical beams by wavelength division multiplexing (WDM) using dichroic optics, scaling up beam power to the kW range and maintaining optical beam quality.

The Influence of Magnetic Field on Pulse Distribution of Laser Diode

The characteristics of a semiconductor laser diode (LD) are highly dependent on the magnetic field that applied on it. This study is valuable in several fields, including the existence of a magnetic field especially in a narrow region, which is difficult to detect by traditional techniques. This will lead to manufacture a micro-sensor to measure a weak magnetic field. In this study, we have investigated the influence of magnetic field, with an amplitude of (zero – 0.55 T) on dynamical characteristics of semiconductor laser diode. This magnetic field has applied parallel and perpendicular on the axis of the active region of the laser diode (LD) chip. The LD used in this study is (Sanyo DL3149-056. ALGanP Index Guided Multiple Quantum will active laser and had threshold current of 11.15 mA and slope efficiency of 189.4 mW/A). It has been found that the full width half-maximum (FWHN), and the peak channel number (PCN) shift, were all increasing with the increased of magnetic field. Finally, the results show that while the peak of the pulse (light intensity) reduces with the increasing of magnetic field, the appearance of more than one peak (abnormalities) on the laser pulse has been founded clearly.

Packaging for Laser-Based White Lighting: Status and Perspectives

AbstractLight-emitting diodes (LEDs) have gained wide adoption in general illumination applications in the last decade. However, the efficiency drop of LEDs with increasing current density limits the luminous flux per wafer area. In contrast, laser diodes (LDs) can achieve higher efficiency at high current density. Likewise, the etendue of LDs is very low due to the small emitting area and divergent angle, facilitating the high-luminance. Hence, LDs may outperform LEDs in future high-luminance solid-state lighting (SSL). However, the rapid development of high-luminance white laser diode (WLD) is still facing some challenges. First, the heat flux of LD chip is extremely high, leading to a higher junction temperature. Second, the laser beam exhibits an elliptical and astigmatic pattern with Gaussian intensity distribution, which may deteriorate the lighting performances. Third, to achieve high-luminance lighting, the laser beam is usually focused onto the phosphor layer, which may easily increase the phosphor temperature to the thermal quenching region. A comprehensive understanding of these problems enables the advancements of packaging designs for WLDs. In this review, we summarized the recent progress in the packaging of WLDs. First, the advantages and applications of LDs were presented. Then, the state-of-the-art methods of generating white light using LDs were reviewed, in terms of packaging structures and performances. Finally, the challenges and corresponding progresses for the packaging of WLDs were overviewed. This review intends to contribute to the development of next-generation high-luminance laser-based white lighting.

Current-feedback-stabilized laser system for quantum simulation experiments using Yb clock transition at 578 nm.

We developed a laser system for the spectroscopy of the clock transition in ytterbium (Yb) atoms at 578 nm based on an interference-filter stabilized external-cavity diode laser (IFDL) emitting at 1156 nm. Owing to the improved frequency-to-current response of the laser-diode chip and the less sensitivity of the IFDL to mechanical perturbations, we succeeded in stabilizing the frequency to a high-finesse ultra-low-expansion glass cavity with a simple current feedback system. Using this laser system, we performed high-resolution clock spectroscopy of Yb and found that the linewidth of the stabilized laser was less than 320 Hz.

Improving the spectral performance of extended cavity diode lasers using angled-facet laser diode chips

We present and compare theoretical and experimental results on the electro-optical performance of extended cavity diode lasers (ECDLs) that employ two ridge waveguide designs for the single-transverse mode GaAs laser diode chip. One facet of the laser diode chips serves as a partially reflective output coupler for the laser cavity. The other facet constitutes an intra-cavity interface which introduces spurious optical feedback to the laser diode chip. The waveguide designs differ with respect to the suppression of this spurious feedback. The first design employs a straight ridge waveguide intersecting both facets at normal incidence. The intra-cavity facet is anti-reflection coated and features a residual intensity reflectivity of the order $$10^{-4}$$ . The second design employs a bent ridge waveguide intersecting the anti-reflection-coated intra-cavity facet at an appropriate angle. This provides an additional suppression of the spurious intensity reflection to a value estimated to be less than $$10^{-6}$$ . We compare the electro-optical performance of both designs theoretically and experimentally. The utilization of a bent waveguide results in an improved spectral stability and purity, specifically a higher side mode suppression and a small intrinsic spectral linewidth over the whole investigated current range, of the external cavity diode laser without sacrificing other parameters such as the output power. The external cavity diode lasers under study exhibit no degradation of the measured frequency noise power spectra and intrinsic linewidths even if there is a drop of the side mode suppression ratio provided that it is not reduced to a very small value. Thus, the usage of a more readily accessible straight waveguide chip in an ECDL could be sufficient if only a limited tuning range and a particularly compact assembly are needed. For spectroscopic applications requiring a small intrinsic spectral linewidth over a large frequency range a bent waveguide chip could be the better choice.

Electrically pumped photonic integrated soliton microcomb

Microcombs provide a path to broad-bandwidth integrated frequency combs with low power consumption, which are compatible with wafer-scale fabrication. Yet, electrically-driven, photonic chip-based microcombs are inhibited by the required high threshold power and the frequency agility of the laser for soliton initiation. Here we demonstrate an electrically-driven soliton microcomb by coupling a III–V-material-based (indium phosphide) multiple-longitudinal-mode laser diode chip to a high-Q silicon nitride microresonator fabricated using the photonic Damascene process. The laser diode is self-injection locked to the microresonator, which is accompanied by the narrowing of the laser linewidth, and the simultaneous formation of dissipative Kerr solitons. By tuning the laser diode current, we observe transitions from modulation instability, breather solitons, to single-soliton states. The system operating at an electronically-detectable sub-100-GHz mode spacing requires less than 1 Watt of electrical power, can fit in a volume of ca. 1 cm3, and does not require on-chip filters and heaters, thus simplifying the integrated microcomb.

Intensity noise in high-frequency range of an external cavity diode laser and its reduction by second harmonic generation.

Characteristics of intensity noise of optically pumped vertical-cavity surface-emitting lasers and solid-state lasers, induced by the beating of the main lasing mode and non-lasing side modes and its reduction, have been reported in recent years. The mode beating noise of an external cavity diode laser composed of an electrically pumped edge-emitting laser diode chip is studied experimentally in this Letter. The noises due to the beating of the main mode with the first- to third-order side modes are observed, and multiple sub-peaks in the beating noise are measured. It is assumed that the new phenomena are coming from the enhanced four-wave mixing in the longer-active medium. Intensity noise reduction is also demonstrated by using the second harmonic generation of a beta barium borate crystal as a nonlinear absorber.

High-power direct diode laser output by spectral beam combining

We demonstrate a spectral beam combining scheme based on multiple mini-bar stacks, which have more diode laser combining elements, to increase the combined diode laser power and realize equal beam quality in both the fast and slow axes. A spectral beam combining diode laser output of 1130 W is achieved with an operating current of 75 A. When a 9.6X de-magnifying telescope is introduced between the output mirror and the diffraction grating, to restrain cross-talk among diode laser emitters, a 710 W spectral beam combining diode laser output is achieved at the operating current of 70 A, and the beam quality on the fast and slow axes of the combined beam is about 7.5 mm mrad and 7.3 mm mrad respectively. The power reduction is caused by the existence of a couple resonator between the rear facet of the diode laser and the fast axis collimation lens, and it should be eliminated by using diode laser chips with higher front facet transmission efficiency and a fast axis collimation lens with lower residual reflectivity.

单片集成的低暗电流1.3 μm激光二极管和探测器芯片

为了在单片上实现半导体激光二极管与探测器的集成，开展了外延材料生长及结构工艺的设计研究。通过刻蚀工艺引入隔离区的方法制备了集成背光探测器的1.3m InGaAsP/InP半导体激光二极管芯片。管芯的光电性能测试显示，激光二极管具有较低的阈值电流17.62 mA，较高的斜率效率0.13 mW/mA，输出功率可达11 mW；在-0.7 V的反向偏压下，探测器区域对光信号具有良好的线性响应，MPD的光电流超过0.3 mA，在-1.7 V的反向偏压下，暗电流可低至25 nA。