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We demonstrate co-doped phosphor-in-glass (PiG) for high performance white light-emitting diodes (WLEDs) employing reduction of red/green phosphors interaction and antireflection coating (ARC). In this study, the novelties are a suitable selection of the 650-nm red and 540-nm green phosphor materials to reduce the mutual interaction between the emission of green phosphor and the absorption of red phosphor, evidenced by photoluminescence spectroscopy, and then an ARC on both sides of the PiG to reduce Fresnel reflection loss. Therefore, the PiG with high luminous efficiency of 63 lm/W, high color rendering index (CRI) of 96, and less amount of phosphor material are obtained. The overall luminous efficiency of the PiG-based WLED is improved by about 15% and the total amount of phosphors is reduced by about 58%. This proposed of co-doped PiG with excellent performance and less amount of phosphor material usage is essential to meet the economic requirement for high-quality WLEDs indoor lighting applications.

We demonstrate a record net gain of 11-dB in a 34-cm fiber length for 300-nm broadband single-mode Cr-doped crystalline core fibers (CCFs) fabricated by precise laser-heated pedestal growth (LHPG) and tetrahedral chromium (Cr4+) optimization. The core composition of the CCF is a Cr4+-doped: yttrium aluminum garnet (YAG). The record gain achieved is mainly due to (1) precise LHPG of the CCFs to fabricate a longer fiber length of 34-cm employing a novel predictive control to constantly maintain conical molten-zone shape in the growth process and (2) the Cr4+ concentration optimization up to 150% utilizing thicker dielectric coating and thermal annealing and then the Cr4+ optimization by polarization pumping. The net gains of 6.4 and 11-dB are measured with and without Cr4+ optimization, respectively. The 72% of net gain improvement is directly related to Cr4+ optimization in the CCFs, as evidenced by SQUID and EPMA measurements, whereas the optimized thicker coating of the Cr4+ concentration provided the dominant net gain improvement of 33% in the CCFs. The development of the CCF is essential for practical use in the next-generation broadband fiber amplifier applications.

High color rendering index (CRI) of 97 and wide correlated-color temperatures (CCTs) range of 2100–7600 K in white light-emitting diodes (WLEDs) employing the two-inch diameter of CaAlSiN3: Eu2+ (red phosphor) and Lu3Al5O12: Ce3+ (green phosphor) co-doped phosphor-in-glass (PiG) are demonstrated by a novel wet-type cold isostatic pressing (CIP) technique. The wet-type CIP enable to apply isostatic pressure to a powder sample in all directions to obtain the PiG with excellent optical properties, high reliability, and thermal stability. The high CRI of 97 and the wide CCTs range of 2100–7600 K achieved are mainly due to the optimized phosphor materials and the precise adjustment thickness of the PiG. Based on the best formula of two-inch diameter PiG and a unique process of wet-type CIP, we have successfully fabricated and demonstrated the good uniformity and excellent performances of a large diameter of two-inch PiG. The proposed of a large diameter of two-inch PiG with excellent performance, high reliability, and thermal stability is essential to meet the economic dimension requirement for commercial usages in high-quality WLEDs indoor lighting applications.

High reliability and luminance of the color wheel in a laser light engine (LLE) employing novel phosphor-in-inorganic silicone (PiIS) fabricated at the low temperature of 180°C for laser projector applications is presented and demonstrated for the first time. Yellow (Y3Al5O12:Ce3+) and green (Lu3Al5O12:Ce3+) phosphors were uniformly mixed by inorganic silicone, organic silicone, and glass to fabricate as a phosphor color wheel. The PiIS-based color wheels showed better thermal stability than the phosphor-in-organic silicone (PiOS), about 3-7 times less lumen loss and 7-8 times less chromaticity shift under accelerated aging at 350°C for 1008 hours. The advantage of the PiIS fabricated at a low temperature of 180°C enabled the achievement of excellent thermal performance, which was similar to the phosphor-in-glass (PiG) fabricated at a high temperature of 680°C. The good thermal stability of the PiIS can be attributed to the high glass melting temperature of up to 510°C. Low-temperature fabrication, excellent optical performance, and high reliability of the proposed PiIS-based color wheels benefit as promising candidates to replace the current PiOS or PIG-based color wheels in the LLE modules for the next-generation laser projector applications.

Tetrahedral chromium (Cr4+)-ions is the main contributor to gain in the broadband single-mode Cr-doped crystalline core fibers (SCCFs). We have demonstrated a gross gain of 8-dB on a length of 27-cm for a 300-nm broadband SCCF using a thermal annealing technique. Gross gain and fiber length are the highest yet reported for the SCCF. The record gain is mainly due to both the longer fiber by aligned molten-zone growth and Cr4+-ions enhancement by thermal annealing. The enhancement mechanism of the Cr4+-ions in the SCCF is experimentally verified by the means of superconducting quantum interference device (SQUID) and electron probe X-ray micro-analysis (EPMA). As a practical application of the proposed 8-dB gain in the SCCFs in fiber transmissions, a 25-Gb/s error-floor free link is successfully demonstrated.

A novel laser-assisted LED for adaptive-driving-beam (ADB) headlights employing an ultra-reliable Ce3+: YAG-based single crystal phosphor (SCP)-converter layer for use in autonomous vehicles is demonstrated. The SCP fabricated at a high-temperature of 1,940°C exhibited better thermal stability than other phosphor-converter materials, evidenced by a thermal aging test. The high-beam pattern of the ADB is measured at a luminous intensity of 88,436 cd at 0°, 69,393 cd at ± 2.5°, and 42,942 cd at ± 5°, which well satisfies the ECE R112 class B regulation. The advantage of introducing the laser-assisted LED system employing the highly reliable SCP is to produce the high intensity for the ADB, which enables the increase of the field of view by 20% and the brightness by 28% for the ADB headlight and results in improving the visibility from ± 7° to ± 8.5° and the illumination distance up to 200 m. This proposed advance ADB headlight with the ultra-reliable SCP and the novel laser-assisted LED is favorable as one of the most promising ADB light source candidates for use in the next-generation autonomous vehicle applications.

A new scheme of advanced driving beam (ADB) module employing ultra-reliable Ce: YAG-based single crystal phosphor (SCP) for use in autonomous vehicles is demonstrated. The Ce: YAG-based SCP layers fabricated by high-temperature of 1500°C exhibits excellent thermal stability. The ADB module consists of a Nichia blue LED with silicone-based phosphor, a digit mirror device (DMD), a projection lens, and two Nichia laser diodes with a Ce: YAG-based SCP layer. The ADB pattern is measured to be 88,436 luminous intensity at 0°, 69,393 cd at ± 2.5°, and 42,942 cd at ± 5°, which are well satisfied the ECE R112 class B regulation. The proposed high-performance ADB module with ultra-reliable Ce: YAG-based SCP layer is favorable as one of the promising ADB module candidates for use in the next-generation automobile headlight applications.

We report a harmonic dissipative soliton 1.93 μm thulium fiber laser based on a tungsten disulfide (WS2) saturable absorber (SA) in the anomalous dispersion regime. The multilayer WS2 nanosheets were prepared by liquid phase exfoliation method and the SA was fabricated by dropping WS2 solution onto a gold mirror. The transferred WS2 SA had a modulation depth of 2.5% and a saturation intensity of 0.82 MW/cm2. By incorporating the SA into a linear Tm3+ fiber laser cavity, harmonic mode-locked dissipative soliton laser was achieved at 1930 nm with the spectral width of 8 nm, the pulse energy of 3 nJ, the pulse width of 3.6 ns, and the repetition rate of 56.3 MHz. Based on the experimental results, it is shown that with the presence of harmonic mode-locking in 2 μm wavelength region, the multilayer WS2 serving as a SA was verified to be a good candidate for broadband high-energy mode-locking. The order of the harmonic dissipative soliton mode-locked pulses remains the same along with the increasing pump power.

We report a harmonic dissipative soliton $1.93~\mu \text{m}$ thulium fiber laser based on a tungsten disulfide (WS2) saturable absorber (SA) in the anomalous dispersion regime. The multilayer WS2 nanosheets were prepared by liquid phase exfoliation method and the SA was fabricated by dropping WS2 solution onto a gold mirror. The transferred WS2 SA had a modulation depth of 2.5% and a saturation intensity of 0.82 MW/cm2. By incorporating the SA into a linear Tm3+ fiber laser cavity, harmonic mode-locked dissipative soliton laser was achieved at 1930 nm with the spectral width of 8 nm, the pulse energy of 3 nJ, the pulse width of 3.6 ns, and the repetition rate of 56.3 MHz. Based on the experimental results, it is shown that with the presence of harmonic mode-locking in $2~\mu \text{m}$ wavelength region, the multilayer WS2 serving as a SA was verified to be a good candidate for broadband high-energy mode-locking. The order of the harmonic dissipative soliton mode-locked pulses remains the same along with the increasing pump power.

The 1400-nm ultrafast mode-locked Cr-doped fiber lasers (MLCDFLs) employing new scheme of single-mode chromium-doped fiber (SMCDF) as optical gain and reduced graphene-oxide (RGO) as saturable absorber is demonstrated for the first time. The output pulse width, average output power, and repetition rate were 118-fs, 2.95-mW, and 15.9-MHz, respectively.

We report gross gain of 10.7-dB for 300-nm broadband single-mode Cr-doped crystalline core fiber (SMCCDF) employing dielectric coating, thermal annealing, and polarization pumping techniques. This gross gain is the highest yet demonstrated of the SMCDCCFs.

A 16-channel silicon photonics transmitter module has been proposed and demonstrated. To prove the feasibility of the module design, it’s necessary to analyze optical coupling calculation, thermal effect, and high-speed signal integrity.

High color rendering index (CRI) and wide correlated color temperatures (CCTs) white LEDs (WLEDs) employing CaAlSiN

A 16-channel optical transmitter module that integrates a silicon photonics chip with Mach-Zehnder modulators (MZMs), a V-groove with single-mode fiber (SMF), micro lens, O-band high-power distributed feedback laser diodes (DFB LDs), and the temperature controller has been proposed and demonstrated. To prove the feasibility of the module design, the optical coupling calculation, the thermal effect, and high-speed signal integrity are analyzed and characterized. The coupling efficiency of optical system is around 45%. The operation temperature of the module can be separately controlled at 30 °C and 35 °C for the silicon photonics chip and DFB LDs by thermal simulation. The 3-dB bandwidth is excess of 40 GHz which allows the module to operate at 50 GBaud signal quality by four-level pulse amplitude modulation (PAM-4). The hybrid assembly technique and modularized solution can meet high-density and high-speed I/O interconnection packaging requirements for silicon photonics device development and also can be applied in the next-generation optical transceivers for high-speed data centers and cloud networks.

An automatically power-stabilized (with power fluctuation

We report gross gain of 8.4-dB for 300-nm broadband single-mode Cr-doped crystalline core fiber (SMCCDF) employing dielectric coating, thermal annealing, and polarization pumping techniques. This gross gain is the highest yet demonstrated of the SMCDCCFs.

We demonstrate a real-time microanalysis approach to the evaporation rate of a (sub)picoliter liquid drop, measured over a 7.85-0.38 picoliter volume, using an off-axis fiber interferometer and achieving the best displacement resolution of 24 nm.

The LiDAR-embedded smart laser headlight module employing a single digital micromirror device is demonstrated. This novel scheme enables reduction in optical components and module space requirements for use in the next-generation high-performance autonomous vehicles.

Higher gain of single-mode Cr-doped crystalline core fibers (SMCDCCFs) with longer fiber length employing an optimized molten-zone in laser-heated pedestal growth (LHPG) technique is demonstrated. The optimized molten zone in the LHPG is determined by an empirical formula. The SMCDCCFs exhibit a length of 24-cm, a core diameter of 25-μm, and a V-value of 2.40 which confirms the LP01 single-mode operation. A 6.44-dB gross gain and a 4.44-dB net gain with 24-cm fiber length of the SMCDCCF at wavelength of 1.4-μm were obtained. Further studies on higher gain of more than 10-dB gross gain of the SMCDCCFs including a longer length of 30-cm, a lower loss fiber, and a suitable annealing technique are essential to develop the SMCDCCFs as broadband fiber amplifiers for practical use in the next-generation fiber transmission systems and are currently under investigation.

A headlight module embedding smart laser headlights and a LiDAR is presented. The headlights include blue lasers for the high beam, and blue LEDs for the low beam, each with a high efficiency glass phosphor-converter we have fabricated. The LiDAR is an indirect-mode time-of-flight 905-nm rangefinder. We used two Nichia GaN lasers emitting a total 9.5-W optical power at 445-nm for the high-beam headlight, and five OSRAM GaN LED emitting a total 12-W at 445-nm for the low-beam headlight. The yellow-converter phosphor is a glass-based Ce3+: YAG slab, 100-mm dia. and 0.2-mm thick, that we have fabricated at 750°C temperature, obtaining a high thermal stability, a high conversion efficiency, and a good color rendering index. A digital micromirror device (DMD) placed in the focus of the parabolic reflector is used to switch off sectors of the high-beam when crossing other vehicles. The 2D image of a CCD camera and the LiDAR data are fed to an image processing unit based on CNN that classifies the targets. The headlight module has a >85% detection accuracy of a pedestrian up to 20 m distance.

Lidar, radar, optical imaging and ultrasonic are important environmental sensing technologies in the field of autonomous driving. Among them, the radar can perform long-distance sensing, however it is limited by the resolution and cannot distinguish objects. Optical images have clear object resolving power, but hardly to get distance information. Ultrasonic only detect objects that are in very short distances. Therefore, it is necessary to have a technique that can clearly distinguish the objects and get the object information such as speed and distance at medium-range (100-m) for autonomous driving scheme entering level 4 and level 5. The existing light technology in the autonomous driving is to place the Lidar module on the roof of a car and perform environment sensing in a rotating manner. Such technology has low sensing capability and is not conform to the development direction of the vehicle industry that not fulfill the demand of autonomous car. In contrast to Lidar module on the roof, placing the Lidar on the front of the car has many advantages, such as easy to collect dust, suffer water corrosion and difficult to set up the electrical system. Integrating the Lidar with headlight system is a feasible direction to solve the aforementioned problems. In this study, we will develop laser headlights system with Lidar module by integrating the optical system of Lidar into headlight a unit, in which the smart laser headlight was achieved by feedback control orders system. The laser headlight will focus on the development of smart headlights with laser as the light source. With the feedback of the system, it can control the car's light field, avoid high-reflection areas at night. The integrated Lidar module will develop a quasi-static optical scanning system with a wavelength of 1550 nm and embed it in the optical path of the laser headlight. By wavelength differences, the optical path of Lidar does not interfere with headlight and high quality optical data could be obtained. Despite adapting 905 nm as optical wavelength in the current technology, the 1550 nm wavelength selected by this study meets the safety regulations and will not cause damage to the human eye at night or during the day. In this study, we will develop a Lidar module attached to a 10W laser headlight for autonomous driving. The simulation and optical performance of integration of Lidar module with laser headlight will be presented.

A new scheme of ultra-fast mode-locked laser (MLL) employing broadband single mode Cr-doped fiber (SMCDF) and multilayer graphene is experimentally investigated. This is the first time report of broadband SMCDF and stacked graphene used in the MLLs. The advantage and performance of ultra-fast MLLs will be reported.

The channelized filtering of orthogonally polarized data streams mixed with 4-GHz 8-QAM-OFDM and NRZ-OOK formats up to 50 Gbps in the C-rich SiC x , micro-ring/bus waveguide is performed with employing the mode-distinguished notch transmittance of mirco-ring.

An advanced laser headlight module (LHM) employing highly reliable glass phosphor is demonstrated. The novel glass-based YAG phosphor-converter layers fabricated by low-temperature of 750°C exhibited better thermal stability. The LHM consisted of a 5 × 1 blue laser diode array, an aspherical lens, a glass phosphor-converter layer with an aluminum thermal dissipation substrate, and a dichroic filter to allow pass blue light and reflect yellow phosphor light. The 5 × 1 blue laser array was packaged with five blue lasers having optical power of 1.2 W per laser. The LHM exhibited total output optical power of 6 W, luminous flux of 1860 lm, relative color temperature of 4100 K, and efficiency of more than 310 lm/W. The high-beam patterns of the LHMs were measured to be 45,000 luminous intensity (cd) at 0°, 31,000 cd at ± 2.5°, and 12,500 cd at ± 5°, which were well satisfied the ECE R112 class B regulation. The proposed high-performance LHM with highly reliable glass-based phosphor-converter layer fabricated by low temperature is favorable as one of the promising LHM candidates for use in the next-generation automobile headlight applications.

Gain enhancement of single-mode Cr-doped crystalline core fiber (SMCDCCF) with longer fiber length fabricated by online laser-heated pedestal growth (LHPG) technique is demonstrated. In comparison with the SMCDCCF fabricated without online growth, the online technique enables real-time monitoring and controlling small molten zone in the LHPG to achieve longer length with better uniformity and smaller core diameter of the SMCDCCFs. The SMCDCCF exhibits a length of 10.6 cm, a core diameter of 25 mu m, and a V-value of 2.40, which confirms the LP01 single-mode operation by the far-field pattern measurement. A 3.9-dB gross gain and a 1.9-dB net gain of the SMCDCCF at the wavelength of 1400 nm were obtained. The gross and net gains are the highest yet reported of the SMCDCCFs. Further development on higher gain of the SMCDCCF may be functioned the SMCDCCF as a broadband fiber amplifier for use in the next-generation fiber transmission systems.

An oriented-dependence-microlens (ODM) visual alignment and packaging for lasers coupling to polarization-maintaining-fibers (PMFs) is proposed and demonstrated. The ODM is fabricated by automatic grinding and accurate positioning techniques. The position accuracy of the grinding machine is ±1°, which is less than the aligned and fabricated angular tolerance of ±2° for the ODM necessary to achieve both high coupling of 80% and high polarized extinction ratio of 30 dB. This indicates that the ODM endface of the fast axis can be visually observed and then surface feature aligned to the axis of the laser polarization direction. A practical package of laser/PMF with compact size and a few components employing the ODM is also demonstrated. The proposed ODM with visually precise surface feature alignment to achieve both high coupling and polarization is beneficial for the application of laser/PMF modules for use in high-precision fiber optic gyroscopes and many high-performance and low-cost lightwave interconnections.

An experimental coupling mechanism is presented that demonstrates efficient coupling between a high-power 980-nm laser diode and a lensed fiber by employing mode (spot size and wavefront) matching in the near-field regime. The results show that the beam spot pattern of the lensed fiber of a horizontally elliptical shape is spot-size matched to the laser. The wavefront of the lensed fiber with a minor radius of curvature ranging from −9 to $10~\mu \text{m}$ exhibits a curve wave that is also phase matched to the laser. This indicates that the similarity in the mode patterns of both the spot size and the wavefront between lensed fiber and laser is responsible for mode-matched beam coupling, leading to a coupling efficiency of more than 80%. In contrast to the lensed fiber, the spot-size of the cleaved fiber is round, and the wavefront is a plane wave. The different mode distributions between the laser and the cleaved fiber lead to a mode mismatch, resulting in a coupling efficiency of lower than 40%. This experimental coupling mechanism investigation in the near-field regime provides useful information for practical micro-optic design with better mode matching to achieve efficient coupling from active to passive components for interconnect applications.

High color rendering index (CRI) and wide correlated color temperatures (CCTs) white LEDs (WLEDs) employing CaAlSiN3: Eu2+ and Lu3Al5O12: Ce3+ co-doped phosphor-in-glass (PiG) are demonstrated. Through fabrication using a low sintering temperature of 620°C to minimize inter-diffusion between the red phosphor and glass, and adjusting thickness of 0.5-0.7 mm to obtain the chromaticity tailorable co-doped PiG, the WLEDs exhibit high CRI of 94 and wide CCTs of 3900 K to 5300 K. This CRI is the highest yet reported for the co-doped PiG. The proposed of the co-doped PiG with good thermal stability fabricated by using a low sintering temperature may provide a novel technique to achieve high-performance WLEDs with high CRI for use in many high-quality of indoor lighting applications, especially in color inspection, clinical inspection, and gallery lighting.