Silicon Multiplexer Research Articles

Polarization multiplexing silicon photonic optical phased array with a wide scanning range.

We propose and experimentally demonstrate a polarization multiplexed silicon optical phased array (OPA) with a wide scanning range. The two polarization states share the same power splitter tree and the phase shifter array. A polarization switch is introduced in front of the power splitter tree to manipulate the polarization state of the light in OPA. Through a polarization splitter-rotator (PSR), the light of two polarization states propagates into the superlattice grating antenna array. The wavelength tuning efficiency could be doubled by optimizing the parameters of the waveguide grating. We demonstrate the scheme on the commonly used 220 nm silicon-on-insulator (SOI) platform. Experimental results indicate that the 24.8° vertical scanning range could be realized with a high wavelength tuning efficiency of 0.31°/nm. The measured field of view (FOV) is 24.8 × 60°.

Design and experimental demonstration of a silicon multi-dimensional (de)multiplexer for wavelength-, mode- and polarization-division (de)multiplexing

Leveraging the physical dimensions of an optical carrier (e.g., wavelength, mode, or polarization) allows significant scaling of the transmission capacity for optical communications. Here we propose a scheme for implementing on-chip silicon (de)multiplexers with simultaneous wavelength-, mode-, and polarization-division (de)multiplexing capability. The device is constructed by using cascaded subwavelength grating (SWG)-based contra-directional couplers. To verify the feasibility of the proposed structure, we perform a proof-of-concept experiment of an 8-channel (de)multiplexer with two wavelengths, two modes, and two polarizations. The insertion losses are lower than 6.6 dB and the crosstalk values are below -18.7dB at around 1540 nm and 1550 nm for all the eight channels.

Using the noise-equivalent temperature difference to compare superlarge photoreceivers based on quantum-well multilayer structures

A method has been developed for analyzing the temperature resolution of far-IR and mid-IR photoreceivers. The features of creating silicon multiplexers for such photoreceivers are discussed. The noise-equivalent temperature difference is analyzed for IR photoreceivers based on silicon multiplexers with framewise accumulation from photodetectors based on quantum-well multilayer structures. The silicon multiplexers thus developed are compared in order to use photosensitive chips, including those with increased dark currents, to create IR photoreceivers with temperature resolution at the response level of similar photoreceivers from leading companies. The structural–technological principles of the creation of mosaic photoreceivers are developed for the case of superhigh size. The technological level thus achieved is discussed for high-precision microassembly of submodule chips into mosaic photoreceivers. Methods are proposed for forming the multispectral photosensitivity response of the mosaic photoreceivers. A comparative analysis is carried out of the size of the “blind zone” of different defining materials.

A Megapixel Matrix Photodetector of the Middle Infrared Range

Abstract—The characteristics of MWIRs focal plane aeeays made in the form of a hybrid chip based on a planar n+–p-HgCdTe focal matrix with 2048 × 2048 elements and a silicon multiplexer are considered. The temperature dependence of the reverse current of elements in the 125–300 K range had a characteristic Arrhenius dependence with an activation energy close to the band gap of the semiconductor and was limited by the diffusion component of the current. At a lower temperature, the current was limited by the generation of carriers with the participation of a deep level near the middle of the forbidden band. The histogram of the detectability of the elements of the matrix had the form of a symmetric curve with a maximum and an average value ≈ 1.3 × 1012 cm Hz1/2/W.

25 × 50 Gbps wavelength division multiplexing silicon photonics receiver chip based on a silicon nanowire-arrayed waveguide grating

A high-performance monolithic integrated wavelength division multiplexing silicon (Si) photonics receiver chip is fabricated on a silicon-on-insulator platform. The receiver chip has a 25-channel Si nanowire-arrayed waveguide grating, and each channel is integrated with a high-speed waveguide Ge-on-Si photodetector. The central wavelength, optical insertion loss, and cross talk of the array waveguide grating are 1550.6 nm, 5–8 dB, and −12–−15 dB, respectively. The photodetectors show low dark current density of 16.9 mA/cm2 at −1 V and a high responsivity of 0.82 A/W at 1550 nm. High bandwidths of 23 and 29 GHz are achieved at 0 and −1 V, respectively. Each channel can operate at 50 Gbps with low input optical power even under zero bias, which realizes an aggregate data rate of 1.25 Tbps.

Three-mode multiplexer and demultiplexer utilizing trident and multimode couplers

In this paper, a simultaneous three-mode silicon (de)multiplexer using a trident coupler and a 3 × 3 multimode interference (MMI) is presented. The fundamental (TE0), first-order (TE1), and second-order (TE2) modes at the input are successfully demultiplexed and converted to three uniform fundamental modes (TE0) at the output ports. The device is designed and optimized by numerical simulation using three-dimensional beam propagation method together with effective index method. The three-mode (de)multiplexing is achieved over the whole C-band with small insertion loss (<0.9 dB) and crosstalk (<−17 dB). The proposed device also features with a small footprint (5μm × 400μm) and a large fabrication tolerance against chip-size variations while maintaining the desired optical performance.

Optimizing the parameters of a system consisting of a photosensitive IR element based on multilayer structures with quantum wells and a silicon photoelectric multiplexer

This paper discusses the design and process principles involved in optimizing the noise-equivalent temperature difference of photodetectors based on multilayer structures with quantum wells in wide ranges of the structural and process limitations of silicon multiplexers, CMOS-technology design norms, and the parameters of photosensitive elements for the long-wavelength IR spectral region.

Analysis of structural–technological limitations in silicon circuits for reading photodiode signals in the IR region

This paper presents the results of a study of the scientific and engineering principles of the creation of silicon multiplexers intended for reading out and preprocessing photodetector signals in the IR ranges 8–14 and 3–5 μm. The noise equivalent temperature difference is estimated for far-IR photodetectors based on silicon multiplexers with linewise and framewise accumulation of signals from HgCdTe photodiodes (PDs). The features of how the structural–technological limitations in the silicon readout circuits affect the characteristics of the IR photodetectors are analyzed for a wide range of parameters of HgCdTe PDs and a wide range of technological design norms for fabricating silicon multiplexers.

Image conversion in uncooled mosaic microbolometer detectors for the IR and terahertz regions with a format up to 3072 × 576 or more

This paper discusses the process-design principles for creating hyperlarge-format mosaic photodetectors (MPDs), based on the butt-joining process of silicon chips with uncooled small-format microbolometer detector arrays (MBDAs). The basic unit is investigated and optimized for the process operations of laser scribing as part of the high-precision butt-joining process of chips in which the process part of the blind zone between the photosensitive edge elements of adjacent MBDA chips has a total size no greater than 30 μm. The design and layout are synthesized for 384×288-format silicon multiplexers, from which a 3072×576-format MPD fabricated using the butt-joining process developed here can provide better than 99% image-conversion efficiency for IR microbolometers and up to 100% for terahertz-range microbolometers.

Increasing the mechanical strength of hybrid photodetectors based on mercury-cadmium-telluride heteroepitaxial layers

Results of the research aimed at improving the strength of hybrid photodetectors (PD) based on mercury-cadmium-telluride heteroepitaxial layers are presented. It is shown that annealing of silicon multiplexers at 157 °C in a hydrogen flow in vacuum changes the shape of indium bumps to hemispherical and levels off their mechanical properties over the plate. Controlled recovery of the natural curvature of silicon multiplexer plates and photosensitive element arrays in hybrid photodetectors at 120 °C extends their operation time. A sequence of technological operations on PD hybridization providing an increase in the efforts needed for separating photosensitive elements from silicon multiplexers at least by 75% compared to the PD with fused indium bumps is proposed.

Manufacturing-oriented developments of silicon multiplexers for multielement IR photodetectors

The architecture of silicon multiplexers for multielement IR photodetectors is considered. A review is given of industrially oriented developments of linear (1 × 32, 1 × 288, 1 × 576) and matrix (32 × 32, 128 × 128, 160 × 128, 320 × 256) silicon multiplexers for mid- and far-IR photodetectors based on cadmium-mercury-tellurium, lead-tin-tellurium, and multilayer structures with quantum wells. An analysis is made of the temperature resolution of matrix IR photodetectors based on multiplexers with row and frame integration of photo signals using micrometer to deep submicron CMOS technologies. Typical parameters of the multiplexer and some of the infrared photodetectors designed at the Rzhanov Institute of Semiconductor Physics, SB RAS are given.

Design features and some implementations of silicon multiplexers for IR photodetectors

This paper discusses the features of the design and organization of silicon multiplexers for linear and array-type IR photodetectors. These have been used as a basis for developing nineteen silicon multiplexers intended for combined operation with multielement photodiode detectors based on mercury–cadmium tellurium compound, with multielement photoresistive detectors based on multilayer quantum-well structures, and other types of photodetectors having spectral sensitivity in the 3–5 and 8–16-μm ranges. The multiplexers can be used as a basis for creating hybrid and monolithic photodetectors of various formats for the mid- and far-IR regions with fairly good temperature resolution (&lt;0.02K).

Performance of Hybrid Laser Diodes Consisting of Silicon Slab and InP/InGaAsP Deep-Ridge Waveguides

The fundamental transverse mode lasing of a hybrid laser diode is a prerequisite for efficient coupling to a single-mode silicon waveguide, which is necessary for a wavelengthdivision multiplexing silicon interconnection. We investigate the lasing mode profile for a hybrid laser diode consisting of silicon slab and InP/InGaAsP deep ridge waveguides. When the thickness of the top silicon is 220 nm, the fundamental transverse mode is lasing in spite of the wide waveguide width of 3.7 μm. The threshold current is 40 mA, and the maximum output power is 5 mW under CW current operation. In the case of a thick top silicon layer (1 μm), the higher modes are lasing. There is no significant difference in the thermal resistance of the two devices.

Analysis of design principles of silicon multiplexer circuits for multielement infrared focal plane arrays

Design principles of silicon multiplexers for linear and matrix infrared (IR) focal plane arrays (FPAs) are considered. Silicon multiplexers intended for operation with multielement mercury-cadmium-tellurium (MCT) photodiode detectors, with multielement photoresistor detectors based on multilayer structures with quantum wells, and with other types of photodetectors sensitive to radiation in the IR ranges from 3 to 5 and from 8 to 16 µm, are discussed. The type and size range of the multiplexers includes 19 models that differ in frame sizes, input circuits, charge capacity, and cell pitch. Around the designed multiplexers, hybrid and monolithic FPAs of various formats for medium and far IR ranges with a rather high temperature resolution (< 0.02 K) have been developed.

A technology for assembling large-format infrared photodetector modules on indium microposts

The initial plane-parallel position of a photodetector array (PDA) and a silicon multiplexer (MUX) is brought about when the tops of the indium microposts are in contact under the action of only the force of gravity on the PDA. We orient the crystals (along xy) in visible light, and we use offset reference marks on the PDAs. We bring chains of laser microholes in the polyimide of the offset reference marks into coincidence with the reference marks on the MUX. We take into account the initial errors of all the axial lines; the alignment error reaches ±0.4μm (along xy). At all stages of the assembly, the MUX is connected, and we observe the touching and the welding of the microposts. To avoid warping the planar transistors (along z), we use stops of suitable height, placed along the perimeter of the PDA.

320×256 photodetector arrays with a built-in short-wavelength cutoff filter

This paper proposes a photodetector design based on a CdHgTe variband heteroepitaxial structure with a high-conductivity layer (HCL) that ensures that the photodiodes have low series resistance and simultaneously serves the function of a short-wavelength cutoff filter. Based on an analysis of how the parameters of the HCL affect the quantum efficiency and the noise-equivalent temperature difference of the photodetector arrays (PDAs), its optimum parameters are determined. Samples of PDAs are fabricated with a format of 320×256 elements for the 8-12-μm spectral range, based on hybrid assembly of photosensitive elements made from p-type (013) HgCdTe/CdTe/ZnTe/GaAs heteroepitaxial structures with an HCL and a silicon multiplexer. The voltage sensitivity, the threshold irradiance, and the noise-equivalent temperature difference at the maximum sensitivity were 4.1×108V/W, 1.02×10−7W/cm2, and 27mK, respectively.

Linear 288×4-format photodetector with a bidirectional time-delay-and-storage regime

Infrared n-p-photodiode photodetectors based on a hybrid assembly of photosensitive elements of format 288×4 with a 56×43-μm step, made from mercury-cadmium telluride heteroepitaxial structures obtained by molecular-beam epitaxy, have been developed, fabricated, and investigated for the 8–12-μm spectral range, along with silicon multiplexers with bidirectional scanning and internal time delay and storage of the signal. The 288×4-format linear photodetector has the following mean values of voltage sensitivity, detectivity, and NETD at the maximum sensitivity: (1–3)×108V∕W, (1.5–2.0)×1011cmHz1∕2W−1, and 9mK, respectively. There are no defective channels.

Investigating processes for forming an infrared CdHgTe-based photodetector in a monolithic version

This paper discusses the results of investigations of processes for forming monolithic integrated cadmium-mercury telluride (CdHgTe)-based IR arrays and their parameters. The processes for growing CdHgTe heteroepitaxial layers (HELs) by molecular-beam epitaxy (MBE) in the cells of a silicon multiplexer have been studied, as well as for forming an n-p junction and contact compounds. For the selective growth of CdHgTe MBE HELs, regimes have been determined for preparing a silicon surface in dielectric windows with dimensions from 30×30to100×100μm. Selective layers of CdHgTe (8μm)∕CdTe(5–7μm)∕ZnTe(0.02μm) have been grown on Si (310). Ion implantation of boron into selective p-type layers has been used to form n-p junctions. Measurements showed that the parameter R0A is 1.25×105Ωcm2 for the spectral range 3–5μm. A monolithic linear array of format 1×32, based on a CdHgTe MBE HEL, has been fabricated by growth in the cells of a silicon multiplexer.

A series of silicon multiplexers for HgCdTe photodiodes of the 8-16-μm spectral range

This paper presents the results of the development of linear (1×288, 1×576) and two-dimensional (128×128, 320×256) silicon multiplexer arrays for HgCdTe photodiodes of the 8–16μm spectral range. Typical parameters of the multiplexers are given, along with the characteristics of long-wavelength hybrid IR photodetectors created at the Institute of Semiconductor Physics of the Siberian Section of the Russian Academy of Sciences.

INDIUM BUMPS SHAPING AND TREATMENT FOR MATRIX PHOTODETECTOR ASSEMBLY BY FLIP CHIP TECHNOLOGY

Indium bumps properties for flip chip assembly of CdHgTe and InAs infrared detector arrays and silicon multiplexer have been investigated. It is shown that the indium bumps fabricated by a vacuum indium deposition and a photolithography, contain a surface layer more rigid in comparison with the bulk indium and having a poor adhesive ability. This layer prevents bumps from the good adhesive contact during assembly and leads to bumps disconnection under a temperature cycling because of the difference in the thermal-expansion coefficients of the infrared detector material and the silicon multiplexer. Designed in this work method of precise removal this layer and subsequent reflow increase the adhesion strength between indium bumps more than order and, thereby, increase the hybrid detector reliability.