Integration Of Photodetectors Research Articles

Optical properties and bridge photodetector integration of lead sulfide nanowires

We studied optical properties and photocurrent characteristics of PbS nanowires grown by chemical vapor deposition. Distinct bandedge photoluminescence (PL) emission was observed in the mid-infrared spectral range and the quantum confinement effect estimated from the PL peak energy was within 40 meV, consistent with the average diameter of the nanowire (∼70 nm) being significantly larger than the exciton Bohr radius (∼18 nm). We also demonstrated interdigit photo detectors making use of these PbS nanowires suspended between two pre-patterned Ti electrodes, where Ti also acted as metal catalyst for the nanowire growth. The threshold wavelength of the photocurrent was found to be ∼3 μm at room temperature.

On-Chip Integration of Photodetector and Sensor: A Multimodal Photonic Device for Sensing Applications

In this paper, we present the design and development of a novel miniaturized multimodal photonic sensor, which can be configured dually as a photodetector in the absorptive mode and as a pyro-detector in the photonic sensor mode. In this paper, we have fabricated a polyvinyl alcohol (PVA) photoactive layer-based MEMS structure and analysed the effect of effective inter-electrode separation on the photoactive area of the photoactive film using the four quadrant metal-semiconductor polymer-metal (MSM) design on the photoresponsivity of this device in terms of photoconductive and the pyroelectric responses. Our analysis reveals that the interdigitated electrode configuration is best suited for photoconductive response while the cross-electrode configuration with large effective inter-electrode spacing is advantageous for pyroelectric measurement in the infrared region. Here, the unique design of this device offers the choice of electrode configurations that enables the utility of this device in various regions of the electromagnetic spectrum. In this regard, we demonstrate the optical detection of localized surface plasmon resonance of immobilized gold nanoparticle monolayer in the visible region, employing the absorptive mode and the detection of the spectroscopic signature of RDX and TNT molecules ( $134~\mu \text{g}$ /cm $^{2})$ in the midinfrared region using photonic sensor mode. This paper paves a way for designing a low-cost PVA-based miniaturized sensor architectures with huge potential for on-chip real-time detections in various fields of scientific and commercial applications.

Characteristics of stacked multi-slot ring resonator sensors

PurposeThis paper aims to develop ring resonator type optical sensors for high-sensitive detection of biomaterials and a solution concentration surrounding sensor devices. The sensing characteristics of a proposed device are investigated.Design/methodology/approachThe proposed device structure is multi-slot ring resonator where the horizontal slots are arranged in vertical direction called as stacked multi-slot ring resonator. The ring resonator consists of silicon nitride because of several advantages such as easy integration of Si photo-detectors. A high sensitivity is expected in this structure because the slot height is precisely controlled by the thickness of stacked silicon nitride and etched silicon oxide layers. Sensing characteristics are evaluated from the simulated effective refractive index using the finite element method and sucrose solution sensing is confirmed using polydimethylsiloxane fluid channel.FindingsIn the simulation for the solution concentration sensor, the detection sensitivity is enhanced with increasing the slot height and the number of slots. On the other hand, for the biomaterial sensor such as the adsorbed antigen-antibody reaction, the sensitivity increases with decreasing the slot height. In this case, more than four times higher sensitivity is expected compared with the slot ring resonator sensor with vertical single slot and 0.1-0.2 μm slot width.Originality/valueThis paper presents an improved new structure of ring resonator type sensors and its optimum design parameters. The sensing characteristics are evaluated, and, for the biomaterial sensor, the sensitivity is high in comparison to the previous slot ring resonator.

Silicon photonics fiber-to-the-home transceiver array based on transfer-printing-based integration of III-V photodetectors.

A 4-channel silicon photonics transceiver array for Point-to-Point (P2P) fiber-to-the-home (FTTH) optical networks at the central office (CO) side is demonstrated. A III-V O-band photodetector array was integrated onto the silicon photonic transmitter through transfer printing technology, showing a polarization-independent responsivity of 0.39 - 0.49 A/W in the O-band. The integrated PDs (30 × 40 μm2 mesa) have a 3 dB bandwidth of 11.5 GHz at -3 V bias. Together with high-speed C-band silicon ring modulators whose bandwidth is up to 15 GHz, operation of the transceiver array at 10 Gbit/s is demonstrated. The use of transfer printing for the integration of the III-V photodetectors allows for an efficient use of III-V material and enables the scalable integration of III-V devices on silicon photonics wafers, thereby reducing their cost.

Attojoule Optoelectronics for Low-Energy Information Processing and Communications

Optics offers unique opportunities for reducing energy in information processing and communications while resolving the problem of interconnect bandwidth density inside machines. Such energy dissipation overall is now at environmentally significant levels; the source of that dissipation is progressively shifting from logic operations to interconnect energies. Without the prospect of substantial reduction in energy per bit communicated, we cannot continue the exponential growth of our use of information. The physics of optics and optoelectronics fundamentally addresses both interconnect energy and bandwidth density, and optics may be the only scalable solution to such problems. Here we summarize the corresponding background, status, opportunities, and research directions for optoelectronic technology and novel optics, including sub-femtojoule devices in waveguide and novel 2D array optical systems. We compare different approaches to low-energy optoelectronic output devices and their scaling, including lasers, modulators and LEDs, optical confinement approaches (such as resonators) to enhance effects, and the benefits of different material choices, including 2D materials and other quantum-confined structures. Beyond the elimination of line charging by the use optical connections, the next major interconnect dissipations are in the electronic circuits for receiver amplifiers, timing recovery and multiplexing. We can address these through the integration of photodetectors to reduce or eliminate receiver circuit energies, free-space optics to eliminate the need for timing and multiplexing circuits (while solving bandwidth density problems), and using optics generally to save power by running large synchronous systems. One target concept is interconnects from ~ 1 cm to ~ 10 m that have the same energy (~ 10fJ/bit) and simplicity as local electrical wires on chip.

Flexible, transparent and ultra-broadband photodetector based on large-area WSe2 film for wearable devices

Although two-dimensional (2D) materials have attracted considerable research interest for use in the development of innovative wearable optoelectronic systems, the integrated optoelectronic performance of 2D materials photodetectors, including flexibility, transparency, broadband response and stability in air, remains quite low to date. Here, we demonstrate a flexible, transparent, high-stability and ultra-broadband photodetector made using large-area and highly-crystalline WSe2 films that were prepared by pulsed-laser deposition (PLD). Benefiting from the 2D physics of WSe2 films, this device exhibits excellent average transparency of 72% in the visible range and superior photoresponse characteristics, including an ultra-broadband detection spectral range from 370 to 1064 nm, reversible photoresponsivity approaching 0.92 A W−1, external quantum efficiency of up to 180% and a relatively fast response time of 0.9 s. The fabricated photodetector also demonstrates outstanding mechanical flexibility and durability in air. Also, because of the wide compatibility of the PLD-grown WSe2 film, we can fabricate various photodetectors on multiple flexible or rigid substrates, and all these devices will exhibit distinctive switching behavior and superior responsivity. These indicate a possible new strategy for the design and integration of flexible, transparent and broadband photodetectors based on large-area WSe2 films, with great potential for practical applications in the wearable optoelectronic devices.

Investigation of the chip to photodetector coupler with subwavelength grating on SOI

We report on two kinds of investigation of the chip to photodetector coupler (CTPC) with uniform and blazed subwavelength grating (SWG) on silicon-on-insulator (SOI) that were conducted for silicon-based hybrid photodetector integration in an arrayed waveguide grating demodulation integrated microsystem. The theoretical model is presented, 3D FDTD and BPM simulations are used to optimize the coupler design. InP/InGaAs photodetector and SOI wafer were integrated through benzocyclobutene bonding. An efficient high-power absorption for TE mode in a broad band is achieved. The power absorption efficiencies of uniform and blazed SWGs in silicon-based hybrid photodetector integration at 1550nm reach 73% and 75%, respectively in the simulation and it reaches as high as 25% in the measurement when coupling the TE-polarized 1550nm light.

Ge Photodetector Monolithically Integrated on Si by Rapid-Melting-Growth Technique

Germanium-based optoelectronic devices have the potential applications in optical communication and detections. In this letter, we demonstrated that high-quality Ge quasi-epilayer can be achieved by rapid-melting-growth and integrated-circuit compatible process. Raman and microscopy techniques revealed that the as-deposited Ge on the silicon substrate became quasi-single crystalline while nanocrystallites embedded within the Ge layer. The Ge/Si heterostructure photodetectors were fabricated with desirable responsivity of 0.22 A/W at −1 V reverse bias and the ratio of photocurrent and dark current is up to 2000 at −0.65 V. This technique demonstrated the possibility of monolithic integration of Ge photodetector for future optical communications at $1.31~\mu \text{m}$ in wavelength with Si electronic circuitry.

Reflective displacement sensors with monolithically integrated VCSELs and RCEPDs

Micro-scale, reflective-type optical displacement sensors have been developed by monolithic integration of vertical cavity surface-emitting lasers (VCSELs) and resonant cavity-enhanced photodetectors (RCEPDs). This compact sensor (700 × 700 μm) consists of an oxide-confined VCSEL that is surrounded by an RCEPD and can measure the linear distance with a measurement range of ~10 mm, which is comparable to that of conventional displacement sensors. Fabrication details and sensor performances are discussed.

A Tutorial on Optical Feeding of Millimeter-Wave Phased Array Antennas for Communication Applications

Given the interference avoidance capacity, high gain, and dynamical reconfigurability, phased array antennas (PAAs) have emerged as a key enabling technology for future broadband mobile applications. This is especially important at millimeter-wave (mm-wave) frequencies, where the high power consumption and significant path loss impose serious range constraints. However, at mm-wave frequencies the phase and amplitude control of the feeding currents of the PAA elements is not a trivial issue because electrical beamforming requires bulky devices and exhibits relatively narrow bandwidth. In order to overcome these limitations, different optical beamforming architectures have been presented. In this paper we review the basic principles of phased arrays and identify the main challenges, that is, integration of high-speed photodetectors with antenna elements and the efficient optical control of both amplitude and phase of the feeding current. After presenting the most important solutions found in the literature, we analyze the impact of the different noise sources on the PAA performance, giving some guidelines for the design of optically fed PAAs.

High-performance binary blazed grating coupler used in silicon-based hybrid photodetector integration

An efficient and high-performance binary blazed grating coupler was designed based on silicon-on-insulator (SOI) used for silicon-based hybrid photodetector integration in an arrayed waveguide grating demodulation integrated microsystem. A relatively high coupling efficiency was obtained to optimize mode matching by the finite-difference time-domain method by choosing appropriate grating parameters, including period, etching depth, and fill factor. Coupling efficiency output at 1550 nm for the TE mode reached 68%. This value was >60% in the wavelength range of 1450 to 1600 nm, specifically 71.4% around 1478 nm. An InP/InGaAs photodetector and SOI wafer were integrated by using benzocyclobutene (BCB) bonding. When the thickness of the BCB bonding layer was 440 nm, power absorption efficiency at 1550 nm for the TE mode reached 78.5%, whereas efficiency reached ∼81.8% around 1475 nm.

Highly efficient polarization-independent grating coupler used in silica-based hybrid photodetector integration

A highly efficient polarization-independent output grating coupler was optimized and designed based on silicon-on-insulator used for silica-based hybrid photodetector integration in an arrayed waveguide grating demodulation-integrated microsystem. The finite-difference time-domain (FDTD) method optimizes coupling efficiency by enabling the design of the grating period, duty cycle, etch depth, grating length, and polarization-dependent loss (PDL). The output coupling efficiencies of both the transverse electric (TE) and transverse magnetic (TM) modes are higher than 60% at 1517 to 1605 nm and ∼ 67% at around 1550 nm. The designed grating exhibits the desired property at the 3-dB bandwidth of 200 nm from 1450 to 1650 nm and a PDL 0.5 dB of 110 nm from 1513 to 1623 nm. The power absorption efficiency at 1550 nm for TE and TM modes reaches 78% and 70%, respectively. Both the power absorption efficiency of TE mode and that of TM mode are over 70% in a broad band of 1491 to 1550 nm.

Light turning mirrors for hybrid integration of SiON-based optical waveguides and photo-detectors

For hybrid integration of an optical chip with an electronic chip containing photo-diodes and processing electronics, light must be coupled from the optical to the electronic chip. This paper presents a method to fabricate quasi-total-internal-reflecting mirrors on an optical chip, placed at an angle of 45° with the chip surface, that enable 90° out-of-plane light coupling between flip-chip bonded chips. The fabrication method utilizes a metal-free, parallel process and is fully compatible with conventional fabrication of optical chips. The mirrors are created using anisotropic etching of 45° facets in a Si substrate, followed by fabrication of the optical structures. After removal of the mirror-defining Si structures by isotropic etching, the obtained interfaces between optical structure and air direct the output from optical waveguides to out-of-plane photo-detectors on the electronic chip, which is aimed to be flip-chip mounted on the optical chip. For transverse-electric (transverse-magnetic) polarization simulations predict a functional loss of 7% (15%), while 7% (18%) is measured.

High-Resolution Broadband Millimeter-Wave Astrophysical Spectrometer with Triple Product Acousto-Optical Processor

An advanced conceptual design of a high-bit-rate triple product acousto-optical processor is presented that can be applied in a number of astrophysical problems. We briefly describe the Large Millimeter Telescope as one of the potential observational infrastructures where the acousto-optical spectrometer can be successfully used. A summary on the study of molecular gas in relatively old (age > 10 Myr) disks around main sequence stars is provided. We have identified this as one of the science cases in which the proposed processor can have a big impact. Then we put forward triple product acousto-optical processor is able to realize algorithm of the space-and-time integrating, which is desirable for a wideband spectrum analysis of radio-wave signals with an improved resolution providing the resolution power of about 105 - 106. It includes 1D-acousto-optic cells as the input devices for a 2D-optical data processing. The importance of this algorithm is based on exploiting the chirp Z-transform technique providing a 2D-Fourier transform of the input signals. The system produces the folded spectrum, accumulating advantages of both space and time integrating. Its frequency bandwidth is practically equal to the bandwidth of transducers inherent in acousto-optical cells. Then, similar processor is able to provide really high frequency resolution, which is practically equal to the reciprocal of the CCD-matrix photo-detector integration time. Here, the current state of developing the triple product acousto-optical processor in frames of the astrophysical instrumentation is shortly discussed.

Hybrid integration of waveguide photodetectors with silicon-on-insulator micro-ring resonator on silicon substrate

To integrate compound semiconductors with foreign substrates can lead to superior or novel functionalities. The design and fabrication of heterogeneously integrated waveguide photodetectors with Silicon-on-Insulator micro-ring resonator are reported in this paper. The micro-ring resonator was fabricated by utilizing electron beam lithography and inductively-coupled-plasma reactive ion etching technique, which is used for wavelength selectivity. The waveguide photodetectors fabricated by wet etching were used for light detection. The free spectral range (FSR) of the hybrid integrated device was about 24nm, and the dark current of 7.9nA was achieved at the reverse bias voltage of 2.0V. The measured response of the photodetector at through port was 0.538μA/W at the wavelength of 1556nm and a reverse bias of 1V.

Self-Aligned Integration of Spin-Coated Organic Light-Emitting Diodes and Photodetectors on a Single Substrate

We present a self-aligned optical all integrated measurement section on a single substrate consisting of an organic light-emitting diode (OLED) as light source and an organic photodetector (OPD), both fabricated by spin-coating. Areas of the layers, that are not required, are removed by an oxygen plasma treatment. No additional shadow mask is used in this self-aligned structuring process as the metal cathodes protect the underlying organic layers. The functionality of the optoelectronic components is maintained. The devices are characterized by current-voltage (I-V) and spectral measurements. The modulation of the OLED light intensity is detected at the OPD by a significant increase of the photo current.

CMOS Technology Scaling Considerations for Multi-Gbps Optical Receivers With Integrated Photodetectors

The integration of photodetectors for optical communication into standard nanoscale CMOS process technologies can enable low cost for emerging high volume short-reach parallel optical communication. Whereas past work has highlighted the challenges that face integrated photodetectors in highly scaled CMOS technologies, this work examines the opportunities afforded by these new technologies. First, scaling promises improved extrinsic photodetector bandwidth thanks to improved TIA performance. Second, modern advanced process features enable new photodetector structures with improved performance. A phototransistor employing deep n-wells is characterized in 65-nm CMOS and exhibits a more than ten-fold increase in responsivity over a similar structure without the buried n-well. Third, equalization techniques benefit from technology scaling and are only just beginning to be applied to CMOS integrated photodetectors. In particular, decision feedback equalization appears to offer potential for 10+ Gbps operation.

Terahertz photomixers based on ultra-wideband horn antennas

Abstract We review recent advances in the development of new terahertz photomixers based on the integration of an ultrafast photodetector with an ultra-wideband transverse electromagnetic wave horn antenna. We expose first a simplified theory of this antenna, the choice of the dimensions and the results of electromagnetic modeling. We expose then the technological process of the antenna and its integration with ultrafast photodetectors. In the last part we present a photomixing experiment and radiation patterns measurements.

On-chip optical interconnection by using integrated III-V laser diode and photodetector with silicon waveguide

On-chip integration of III-V laser diodes and photodetectors with silicon nanowire waveguides is demonstrated. Through flip-chip bonding of GaInNAs/GaAs laser diodes directly onto the silicon substrate, efficient heat dissipation was realized and characteristic temperatures as high as 132K were achieved. Spot-size converters for the laser-to-waveguide coupling were used, with efficiencies greater than 60%. The photodetectors were fabricated by bonding of InGaAs/InP wafers directly to silicon waveguides and formation of metal-semiconductor-metal structures, giving responsivities as high as 0.74 A/W. Both laser diode and the photodetector were integrated with a single silicon waveguide to demonstrate a complete on-chip optical transmission link.

A Comprehensive Review of One-Dimensional Metal-Oxide Nanostructure Photodetectors

One-dimensional (1D) metal-oxide nanostructures are ideal systems for exploring a large number of novel phenomena at the nanoscale and investigating size and dimensionality dependence of nanostructure properties for potential applications. The construction and integration of photodetectors or optical switches based on such nanostructures with tailored geometries have rapidly advanced in recent years. Active 1D nanostructure photodetector elements can be configured either as resistors whose conductions are altered by a charge-transfer process or as field-effect transistors (FET) whose properties can be controlled by applying appropriate potentials onto the gates. Functionalizing the structure surfaces offers another avenue for expanding the sensor capabilities. This article provides a comprehensive review on the state-of-the-art research activities in the photodetector field. It mainly focuses on the metal oxide 1D nanostructures such as ZnO, SnO2, Cu2O, Ga2O3, Fe2O3, In2O3, CdO, CeO2, and their photoresponses. The review begins with a survey of quasi 1D metal-oxide semiconductor nanostructures and the photodetector principle, then shows the recent progresses on several kinds of important metal-oxide nanostructures and their photoresponses and briefly presents some additional prospective metal-oxide 1D nanomaterials. Finally, the review is concluded with some perspectives and outlook on the future developments in this area.