Beam steering devices can be used for various applications such as light detection and ranging and free space optical communication. The conventional methods for the beam steering are based on the mechanical rotation of mirrors and cause bulk form-factor and limited operation speed. The metasurfaces are arrays of dielectric or metallic antennas that can tailor the optical properties such as amplitude and phase at the deep subwavelength range. Here, we present the all-dielectric metasurface that can modulate the reflection phase >270° with high reflectivity >60% as a function of the individually applied voltage in the near infrared regime.
Metasurfaces provide versatile platforms for arbitrary wavefront shaping with designer optical response such as amplitude, phase, and polarization at the deep subwavelength regime. Tunable metasurfaces can bring additional degree of freedom in terms of the time-dependent change of these responses, which can pave a way for novel applications such as wide-field-of-view holographic display and light detection and ranging (LiDAR). In this talk, we present the all-dielectric metasurface array that can modulate the phase of light above 270° in reflection with high reflectivity over 60% as a function of the individually applied voltage in the near infrared regime.
The commoditization of photonics would be possible only with the development of photonic integrated circuits and appropriate volume applications that require them. As such an application, a light detection and ranging(LiDAR) sensor has recently been in strong demand from various applications including autonomous driving. In terms of technology, as silicon photonics enters an industrial phase and begins to utilize the existing CMOS infrastructure, photonic integrated circuits are also expected to enter a virtuous cycle of volume and cost. This work outlines the current status of LiDAR research using the silicon photonics platform in Samsung. Based on the III/V-on-Si technology, Samsung's platform enables the development of chip-scale LiDAR that integrates all photonic devices such as wavelength-tunable laser, semiconductor optical amplifier, and custom optical phased array. With the LiDAR chip in the core, a palm-top LiDAR module prototype including control and signal processing circuits is also presented. Then, initial application-level attempts in autonomous driving are presented in the hope of pathfinding towards the LiDAR commoditization, and more broadly, commoditization of photonics.
For the first time, we present an active 2D metasurface array and its demonstrated versatile beam steering. The array is composed of individually-addressable, gate-controlled 10×10 pixels where each pixel modulates the phase of light in reflection. Each pixel is a gated plasmonic nanoresonator with an indium tin oxide (ITO) layer embedded in its middle. When proper gate biases are applied to the array, the refractive index of the ITO layer changes, generating a phase gradient necessary for dynamic beam steering. By generating a reconfigurable binary phase grating, we have successfully demonstrated full-area, 2D arbitrary beam steering.
We present an electrically tunable metasurface and demonstrate an ultrafast beam steering and distance-ranging. A unit cell of the proposed device consists of plasmonic antennas and an ITO film as an active, tunable layer. By individually applying electrical biases to the top and bottom of the unit cell, we achieve in the near-infrared range a phase change up to 360 degrees while keeping the amplitude constant. An adjustable gradient phase profile allows for all solid-state-electronic beam steering. Using the Time-of-Flight principle, we demonstrate for the first time metaphotonic-light detection and ranging (Meta-LiDAR).
We designed and fabricated a 1.3-um hybrid vertical Resonant-Cavity Light-Emitting Diode for optical interconnect by using direct III-V wafer bonding on silicon on insulator (SOI). The device included InP based front distributed Bragg reflector (DBR), InGaAlAs based active layer, and SOI-based high-contrast-grating (HCG) as a back reflector. 42-uW continuous wave optical power was achieved at 20mA at room temperature.
Optical interconnects may provide solutions to the capacity-bandwidth trade-off of recent memory interface systems. For
cost-effective optical memory interfaces, Samsung Electronics has been developing silicon photonics platforms on
memory-compatible bulk-Si 300-mm wafers. The waveguide of 0.6 dB/mm propagation loss, vertical grating coupler of
2.7 dB coupling loss, modulator of 10 Gbps speed, and Ge/Si photodiode of 12.5 Gbps bandwidth have been achieved on
the bulk-Si platform. 2x6.4 Gbps electrical driver circuits have been also fabricated using a CMOS process.
AlInGaN based blue and blue-green LDs were investigated with regard to the
characteristics of GaN semiconductor laser diodes. High power, single mode blue LDs with
high COD level (~334mW under CW operation at 25°C, kink-free at 150mW) and long lifetime
(~10000 hours under CW operation, 50mW 25°C) were achieved. No significant characteristic
differences between blue LDs on LEO-GaN/sapphire and GaN substrate were observed. The
blue-green LD which has the wavelength of 485 nm was successfully fabricated and
demonstrated under CW operation 25°C, while it showed poor performances of LD
characteristics compared to those of blue LDs. We believe that the poor performance of blue-green
LDs were caused by the piezo-electric effect by lattice mismatch along C-axis of GaN, In
fluctuation by lattice mismatch and In solubility limit in InGaN QWs and thermal annealing
which was performed during the p-layer growth.
We report on the development of GaN-based violet laser diodes (LDs) for the high-capacity optical storage application and blue LDs for the laser projection display application. InGaN LDs with emission wavelength of ~405 nm are already being adopted for next-generation optical-storage systems. We present results on >400 mW single-mode output power under pulsed operation which can be employed in 100 Gbyte multi-layer BD systems. We designed LD layer structures to exhibit high level of catastrophic optical damage (COD) and small beam divergence. In addition, GaN-based blue LDs with emission wavelength of ~450 nm have also been developed for the application to the blue light sources of laser display systems. We demonstrate single-mode blue InGaN LDs with >100 mW CW output power. Interestingly, we observed anomalous temperature characteristics from the blue InGaN LDs, which has shown highly-stable temperature dependence of output power or even negative characteristic temperature (T0) in a certain operation temperature range. This unusual temperature characteristic is attributed to originate from unique carrier transport properties of InGaN QWs with high In composition, which is deduced from the simulation of carrier density and optical gain.
We investigated the dependency of waveguide structures on ripples of far-field patterns in 405nm GaN-based laser diodes theoretically and experimentally. As the n-type cladding layer thickness decreases, the passive waveguide modes strongly interact with an active layer mode. This suggests that the thicknesses of n-AlGaN/GaN superlattice clad and n-GaN waveguide layers have significant influences on FFP ripples. We successfully obtained very smooth far-field patterns perpendicular to the junction plane by optimizing both n-AlGaN/GaN clad layer thickness and n-GaN waveguide layer thickness.
The enhanced output power with improved lifetime is required for the GaN-based blue-violet laser diode (LD) as a light source for Blu-ray Disc or HD-DVD. In this paper, the output power levels and aging behaviors in GaN-based LDs grown on sapphire substrates were compared in epi-up and epi-down bonding. At low current level, the two bondings
show little differences in L-I characteristics. At high current level, however, the epi-up bonding shows a rapidly decreased slope efficiency in L-I characteristics with increasing current injection. On the contrary, the slope efficiency in epi-down bonding is not so much deteriorating as that in epi-up bonding. The differences in junction temperature between epi-up and epi-down bonding are large at higher current levels. The junction temperature of epi-up bonding is
about two times higher than that of epi-down bonding, implying efficient heat dissipation in epi-down bonding. At aging test, the epi-down bonding LD shows lower degradation rate at the aging slope than that of epi-up bonding LD. The degradation rate is accelerated by poor heat dissipation in epi-up bonding. Thus, for the higher power and longer lifetime, it is necessary to employ efficient heat dissipation structures such as epi-down bonding for the GaN-based LD
on sapphire substrate.
O. H. Nam, K. H. Ha, H. Y. Ryu, S. N. Lee, T. H. Chang, K. K. Choi, J. K. Son, J. H. Chae, S. H. Chae, H. S. Paek, Y. J. Sung, T. Sakong, H. G. Kim, H. S. Kim, Y. H. Kim, Y. J. Park
KEYWORDS: Aluminum, Semiconductor lasers, Electron beam lithography, Near field optics, Gallium nitride, Superlattices, Near field, Magnesium, High power lasers, Gallium
High power and high efficiency AlInGaN-based laser diodes with 405 nm were fabricated for the post-DVD applications. Magnesium doped AlGaN/GaN multiple quantum barrier (MQB) layers were introduced into the laser diode structure, which resulted in considerable improvement in lasing performances such as threshold current and slope efficiency. Asymmetric waveguide structure was used in order to improve the characteristics of laser diodes. Aluminum content in the n-cladding layer was varied in connection with the vertical beam divergence angle and COD level. By decreasing Al content in the n-cladding layer, the vertical divergence angle was reduced to 17 degree and the COD level was enhanced to over 300mW. The maximum output power reached as high as 470 mW, the highest value ever reported for the narrow-stripe GaN LDs. In addition, the fundamental transverse-mode operation was clearly demonstrated up to 500 mW-pulsed output power.
With increasing demands for the development of high power GaN-based blue-violet laser diodes (LDs), thermal management has become an important issue. We present a new method to determine junction temperature of GaN-based LDs for simple, fast, and reliable characterization of thermal performances. The large change of forward operation voltage with temperature is advantageously used to measure junction temperature. Using this method, we compare junction temperature of LD structures with different substrates and chip mounting methods. It is found that the junction temperature can be reduced considerably by employing GaN substrates or epi-down bonding. For epi-down bonded LDs, as much as two-fold reduction in junction temperature is achieved compared to epi-up bonded ones and temperature increase in this case is only about 13 degrees for more than 100 mW-output power.
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