Laser Diode Package Research Articles

Interface Contact Thermal Resistance of Die Attach in High-Power Laser Diode Packages

The reliability of packaged laser diodes is heavily dependent on the quality of the die attach. Even a small void or delamination may result in a sudden increase in junction temperature, eventually leading to failure of the operation. The contact thermal resistance at the interface between the die attach and the heat sink plays a critical role in thermal management of high-power laser diode packages. This paper focuses on the investigation of interface contact thermal resistance of the die attach using thermal transient analysis. The structure function of the heat flow path in the T3ster thermal resistance testing experiment is utilized. By analyzing the structure function of the transient thermal characteristics, it was determined that interface thermal resistance between the chip and solder was 0.38 K/W, while the resistance between solder and heat sink was 0.36 K/W. The simulation and measurement results showed excellent agreement, indicating that it is possible to accurately predict the interface contact area of the die attach in the F-mount packaged single emitter laser diode. Additionally, the proportion of interface contact thermal resistance in the total package thermal resistance can be used to evaluate the quality of the die attach.

Design of a single aspheric beam homogenizer for accurate particle sizing application.

Understanding, detection, and accurate monitoring of particles are of utmost importance in various industrial fields and environmental science. Optical sensors allow for real-time monitoring of particles at the single species level by analyzing the elastically scattered light intensities. Nevertheless, since most laser diodes employed for illuminating the particle generally follow a Gaussian-type intensity distribution, the non-uniform energy distribution across the aerosol channel causes considerable errors in the conversion of the scattered light intensities into the actual particle sizes. In order to achieve uniform illumination of particles across the aerosol channel and improve the particle sizing and classification accuracy, we design and customize a single aspheric lens, which efficiently converts the divergent Gaussian beam profile of a TO packaged laser diode into a one-dimensional flattop beam profile along the fast axis at the desired working distance. A beam uniformity better than 5% has been achieved. Furthermore, we demonstrate a practical sensing application using the designed lens for accurate particle sizing, and an obvious improvement in the accuracy has been achieved compared to that based on off-the-shelf aspheric lenses. The singlet beam homogenizer developed in this work has many appealing features (e.g., high uniformity and energy efficiency, compactness, and low stray light), which is especially relevant for building portable particle sensors in order to address various industrial applications where on-site or remote metrology and classification of particles are required.

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.

Research and analysis of voids in semiconductor laser diode packaging reflow soldering

AbstractThe causes of voids in the soldering layer during vacuum reflow soldering of semiconductor laser devices are investigated, as are the movement and change laws of bubbles in the voids under different reflow chamber settings. An ultrasonic scanner is used to test and experiment with a series of 1064 nm wavelength semiconductor lasers. A technique for detecting the void rate based on the wavelength difference is proposed based on the association between the device wavelength, junction temperature, and voids. The average void rate error when comparing measured and calculated values is just 1.5%, demonstrating the validity of this estimation technique for defining the void rate of the device and providing a theoretical and practical reference to analyze the void rate of the device.

Defect Detection for Metal Base of TO-Can Packaged Laser Diode Based on Improved YOLO Algorithm

Defect detection is an important part of the manufacturing process of mechanical products. In order to detect the appearance defects quickly and accurately, a method of defect detection for the metal base of TO-can packaged laser diode (metal TO-base) based on the improved You Only Look Once (YOLO) algorithm named YOLO-SO is proposed in this study. Firstly, convolutional block attention mechanism (CBAM) module was added to the convolutional layer of the backbone network. Then, a random-paste-mosaic (RPM) small object data augmentation module was proposed on the basis of Mosaic algorithm in YOLO-V5. Finally, the K-means++ clustering algorithm was applied to reduce the sensitivity to the initial clustering center, making the positioning more accurate and reducing the network loss. The proposed YOLO-SO model was compared with other object detection algorithms such as YOLO-V3, YOLO-V4, and Faster R-CNN. Experimental results demonstrated that the YOLO-SO model reaches 84.0% mAP, 5.5% higher than the original YOLO-V5 algorithm. Moreover, the YOLO-SO model had clear advantages in terms of the smallest weight size and detection speed of 25 FPS. These advantages make the YOLO-SO model more suitable for the real-time detection of metal TO-base appearance defects.

Native signal self-mix interferometer has less than 1 nm noise equivalent displacement.

We demonstrate that the native configuration of a self-mixing interferometer attains a minimum detectable displacement of 0.72 nm or λ/1870 at the laser wavelength of 1310 nm, obtained by the bare laser diode package including a monitor photodiode, observed in the electrical domain by means of an oscilloscope and without any electronic processing of the signal.

Effect of microstructure of Au80Sn20 solder on the thermal resistance TO56 packaged GaN-based laser diodes

Au80Sn20 alloy is a widely used solder for laser diode packaging. In this paper, the thermal resistance of GaN-based blue laser diodes packaged in TO56 cans were measured by the forward voltage method. The microstructures of Au80Sn20 solder were then investigated to understand the reason for the difference in thermal resistance. It was found that the microstructure with a higher content of Au-rich phase in the center of the solder and a lower content of (Au,Ni)Sn phase at the interface of the solder/heat sink resulted in lower thermal resistance. This is attributed to the lower thermal resistance of Au-rich phase and higher thermal resistance of (Au,Ni)Sn phase.

Hydrolysis kinetic study of CaAlSiN3:Eu2+ red phosphor with both water immersion test and first-principles calculation

At present, most high-power white Light-emitting diode and laser diode (LED&LD) package is usually constructed by a blue LED&LD chip with a Cerium doped Yttrium Aluminum Garnet (YAG:Ce3+) yellow phosphor, but its color rendering performance is severely challenged due to the lack of red light emission spectrum. The CaAlSiN3:Eu2+ red phosphor can effectively improve the color quality of traditional yellow phosphor converted white LED&LDs(pc-wLED&LDs), however, it is often susceptible to degradation under high temperature and high humidity environments, which will directly affect the color quality of pc-wLED&LDs. In this study, a series of water immersion tests on CaAlSiN3:Eu2+ red phosphor are used to quantitatively study its hydrolysis reaction kinetics. Then, the degradations of its photoluminescence and photothermal performances are evaluated by characterizing the crystal structure, micromorphology and chemical element composition. Finally, an atomic level hydrolysis reaction mechanism of CaAlSiN3:Eu2+ red phosphor is investigated by using the first-principles density functional theory (DFT) calculation. The results show that: (1) By modelling the in-situ monitored electrical conductivity of CaAlSiN3:Eu2+ red phosphor water solution with a first-order reaction function, the calculated hydrolysis reaction rate satisfies the Arrhenius relationship and the reaction activation energy is estimated as 49.19 kJ/mol; (2) The increased self-heating effect of CaAlSiN3:Eu2+ red phosphor after water immersion test attribute to its drastic drop of light emission efficiency; (3) The hydrolysis reaction mechanism of CaAlSiN3:Eu2+ red phosphor is confirmed, which sequentially results in the dissolution of Ca2+ and OH−, the crash of host lattice and the accumulation of reaction residues.

C-mount packaged laser diode end-pumped passively Q-switched laser with a microlens as pump coupling component

A microlens has been optimum simulated and designed for an 808 nm laser C-mount packaged semiconductor laser rectangle beam collimation. By designing the suitable focal length, the fast axis light is compressed. After the compression, the fast axis and the slow axis have the same divergence angle, which increases the matching degree between the pump light and the fundamental light. The design for cylinder microlenses collimation system has been discussed in detail. In the laser we designed, the pump source is a C-mount packaged laser diode with controlling the duty cycle of electric pulse. We demonstrate a 63.1 mW, 1 kHz, 779 ps end-pumped Nd:YAG/Cr4+:YAG laser at 1064 nm using the above designed microlens capable of compressing fast axis light.

Microchip laser converter based on InGaN laser diode and (Zn)CdSe quantum dot heterostructure

A high-efficiency microchip violet–green laser converter based on a molecular-beam epitaxy grown green-emitting (Zn)CdSe quantum dot (QD) II–VI laser heterostructure, optically pumped by emission of a cheap violet InGaN laser diode (LD) was demonstrated. The active region of the II–VI laser heterostructure consisted of three electronically coupled (Zn)CdSe QD sheets in a single ZnSe quantum well (QW) placed asymmetrically inside a graded-index ZnMgSSe/ZnSe superlattice optical waveguide. The cavity length of the cleaved-facet II–VI laser was 130 μm which is a nearly optimal value for minimizing the excitation power. InGaN LD radiation was focused into a narrow stripe on the surface of the II–VI laser by a microlens optical system. The converter showed laser emission at 541 nm with threshold excitation power of ∼0.5 W. The maximal output pulse power and conversion efficiency of 1.5 W and ∼15%, respectively, were achieved. The device was mounted in a standard TO-18 LD package. Photograph of the operating violet–green microchip laser converter.

Optically pumped quantum-dot Cd(Zn)Se/ZnSe laser and microchip converter for yellow – green spectral region

The room temperature laser generation in the yellow – green () spectral range has been demonstrated under optical pumping by a pulsed nitrogen laser of quantum dot heterostructures. The maximum achieved laser wavelength was as high as at a laser cavity length of . High values of both the output pulsed power (up to ) and the external differential quantum efficiency () were obtained at a cavity length of . Both a high quality of the laser heterostructure and a low lasing threshold () make it possible to use a pulsed InGaN laser diode as a pump source. A laser microchip converter based on this heterostructure has demonstrated a maximum output pulse power of at . The microchip converter was placed in a standard TO-18 ( in diameter) laser diode package.

Study on Effects of Solder Fluxes on Catastrophic Mirror Damages During Laser Diode Packaging

Solder fluxes have been commonly used in die bonding of high-power semiconductor lasers via indium solder. In this paper, the effects of some fluxes, with respect to reflow duration and cleaning solvent residues on the catastrophic mirror damage (CMD), are investigated. Scanning electron microscopy with an energy dispersive X-ray indicates that an increment of the sites of CMDs, size, and quality, obtained by increasing the reflow duration, depends on the type of the used flux. Fourier transform infrared spectroscopy confirms that nearly no contamination of the flux exists after the cleaning process. X-ray photoelectron spectroscopy analysis revealed that the flux or flux cleaning solvent residues could not be the main source of carbon or carbon compounds on the surface and, hence, the CMDs attributed to them. Finally, indium packaging of a diode laser by means of these rosin fluxes shows that RA flux has the best die bonding quality among other fluxes.

61.2: Cooling Design of High Power Laser Diodes Array Using Channel Flow and Vapor Chamber Method

AbstractThe maximum junction temperature (Tj,max) of high power laser diode array is cooled down by 13% using channel flow method; the junction temperature deviation is also improved by 30% using vapor chamber. With the channel flow design, Tj,max can be lower 6% by introducing air deflector, and lower additional 4% by optimizing the air separator length. With the heat sink aspect ratio optimization, Tj,max can be lower additional 3% by introducing vapor chamber. Furthermore, by the TO‐CAN packaged laser diode device model, the heat path and the distribution of the thermal resistance are thoroughly investigated.

53.3: New Light‐bar Emitting Phosphor‐converted White Line Light Pumped by InGaN/GaN Laser Diode for Edge‐lit Backlight Unit Applications

AbstractA new type of light bar using laser diode for LCD backlight applications is presented. It consists of six white line‐emission units including a high‐power InGaN/GaN laser diode (LD). The LD emits at around 400nm and pumps up phosphors coated on a glass light‐guide stick in the line‐emission unit. It is demonstrated that a prototype of new LD package is capable of more efficient thermal transfer than the conventional CAN‐type ones. The LD light bar has the following advantages: 1) fewer light emitting elements, 2) longer continuous white line emission, 3) higher rate of heat transfer.

Low Cost Vibrometer Utilizing Laser Diode Self-Mixing with Sound Card Controlled by LabVIEW

A compact and versatile vibrometer is designed based on self-mixing laser diode vibrometry interference to measure the oscillation amplitude of a piezoceramics (PZT). A fraction of the light emitted by the laser diode (LD) is reflected by the PZT, and then mixes with the light inside the cavity, causing a modulation of the laser output. The self-mixing signal is detected by the photodiode accommodated in the LD package and acquired by a data acquisition and processing system based on sound card and LabVIEW. Amplitude of the PZT is detected by fringe counting. According to results of test, this device can measure the vibration signal with a measurement accuracy of λ/2. The measurable oscillation amplitude range from 0.325 um to 6.5um

An analysis of transient thermal properties for high power GaN‐based laser diodes

AbstractThermal properties of 405 nm GaN‐based laser diodes were investigated by employing a transient heating response method based on the temperature dependence of diode forward voltage. Thermal resistances of materials consisting of packaged laser diodes were differentiated in transient thermal response curves at a current below threshold current. With a current above threshold current, no significant change in thermal resistances and difference between junction‐up and junction‐down laser diodes was observed at pulses shorter than 3 sec. From an analysis with long current injections, thermal resistance of a packaged laser diode with a junction‐up bonding was ∼45 °C/W which was higher than that of a junction‐down bonded laser diode by ∼10 °C/W. Further analyses based on parameters obtained from voltage recovery curves indicated that the time constant for cooling is directly related to the thermal resistance and thermal capacitance of a laser diode package. (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Sliding Mode Based Fuzzy Control for Positioning of Optical Pickup Head

Abstract A laser diode package is mounted on an optical pickup head actuator. The laser diode package is used to sense the displacement of a moving target by self-mixing interference signals. A sliding mode based fuzzy control method is developed to achieve fast response of the optical pickup head actuator, which is driven in a focusing direction. Simulation results show the proposed method performs better than sliding-mode control. Experimental results further show that the proposed control method outperforms sliding-mode control.

Surface-plasmon-coupled semiconductor diode-laser package for refractive index sensing

We combine plasmonic grating structures with semiconductor laser-diode packages to realize a prototype of miniaturized chemical/biosensor. The advantages of such a device include compact size, low cost, energy effectiveness, long device lifetime, stable performance, and label-free sensing, which should have commercialization potential.

Online measurement and correction of post-weld shift in laser welding packaging for laser diodes

In order to measure and correct post-weld shift (PWS) which is inherent in the laser welding packaging process for laser diodes, a novel method based on strain gauges was proposed to perform online measurement of the welding shift in real time. This method can measure micro-displacement caused by laser welding in two directions with submicrometer accuracy. The direction and magnitude of PWS can be determined from measurement results, and then correction welding is applied to compensate the PWS in prescribed direction. The measurement system was established and experiments of laser welding, PWS measurement, and correction for specially designed laser diode packaging assembly are conducted. Experimental results show that the proposed method is able to measure the PWS accurately in real time, and the coupling light power can be regained to over 90% of the power before welding with laser hammering technique according to measurement results. With advantages of low cost, comparable accuracy, and real-time measurement, the proposed method will be very useful for improving the packaging productivity and performance for widely used transistor outline (TO)-Can style laser diodes.

Laser Diode Feedback Signal for Position Sensing Using Self-Mixing Interference

We modified a digital versatile disk (DVD) pickup head as a DVD actuator with a laser diode package for sensing. Tuning a tilting coil in the DVD actuator causes the tilt of a laser diode to compensate misalignment between a target surface and the laser diode facet. Experimental results show that tuning the tilting coil compensates misalignment between both surfaces to achieve effective self-mixing signal. Furthermore, we present the conformity between the output voltage and the target surface displacement from a laser diode package using the self-mixing effect. The resolution in linear region of self-mixing signal is 100 mV/nm.