Arrayed Waveguide Grating Device Research Articles

Monolithic integration of waveguide amplifiers and passive polymer photonic devices using photolithography

The monolithic integration of rare-earth-doped waveguide amplifiers with passive photonic devices has long been a subject of extensive research. Herein, we propose a method for active-passive monolithic integration based on polymer photonic integrated devices. The monolithic integration of passive devices with active waveguide amplifiers is achieved by spin-coating an active layer atop a passive polymer waveguide and subjecting specific regions of the active layer to selective photolithography. To validate the proposed monolithic integration scheme's impact on the performance of passive devices, performance tests were conducted on both passive and active-passive integrated 8-channel arrayed waveguide grating (AWG) devices. The crosstalk (CT) of the AWG devices before and after adding the active layer ranged from −12.04 dB to −14.72 dB and from −10.02 dB to −14.88 dB, respectively, with channel spacings of 9.29 nm and 8.80 nm, indicating consistent performance of the passive devices with the addition of the active layer. In a 0.5 cm-long active waveguide, internal net gain was achieved across all eight channels of the AWG, with a gain bandwidth ranging from 1518 nm to 1580 nm. Notably, an internal net gain of 9.5 dB was attained at 1527 nm. The successful integration of rare-earth-doped waveguide amplifiers with passive components on a monolithic chip has been achieved for the first time, requiring only two straightforward photolithography steps. This milestone not only preserves the inherent functionality of passive components but also enables effective signal amplification. This technological innovation holds the promise of fully harnessing the potential of rare-earth-doped waveguide amplifiers in the realm of photonic integrated circuits, thereby catalyzing significant breakthroughs and advancements in the field of optoelectronics.

An experimental investigation and multiphysics simulation of thermoelectric temperature controller for AWG chips

The refractive index of silicon-based waveguide materials is highly sensitive to temperature and stress, and the effective refractive index of the waveguide varies with temperature changes. Thus, it is critical to reduce the temperature dependence of Arrayed Waveguide Grating (AWG) devices and to precisely control the center wavelength of AWGs. In this study, the thermoelectric cooler (TEC) was designed and fabricated to control the temperature of the thermal AWG chip, which did not require any material replacement or reprocessing of the AWG chip. Different magnitudes and polarities of voltage are applied to the TEC to regulate its operational state (heating or cooling). A multiphysics simulation model of a thermal AWG device is established and validated through transient and steady-state experiments. This study investigated the influence of different conditions (input voltage, environmental temperature) on the temperature and maximum stress of the AWG chip. A conformal TEC was designed and its performance was compared with that of the square TEC. The energy consumption of the conformal TEC was also tested and analyzed. The results show that in a 25 °C ambient environment, the TEC can control the temperature of the AWG chip in the range of 1.5–78.3 °C, significantly expanding the current operational temperature range of 65.0–85.0 °C when using Positive Temperature Coefficient (PTC) heaters. Under the same conditions, when using the conformal TEC as the temperature control device, the temperature gradient on the AWG chip is reduced by 1.37 °C during cooling and 2.80 °C during heating. The maximum stress value in the core layer is always lower, with a maximum reduction of 3.61 MPa. TEC can set the ideal operating temperature of the AWG chip according to the actual operating environment of the product, which reduces the energy consumption of TEC. A comparison is made between the average power consumption of the conformal TEC and the PTC heater under two operating conditions: a 25 °C constant-temperature environment and a natural environment. The average power consumption can be reduced by up to 97.87 % and 93.02 %, respectively. This study holds significant guidance for solving the temperature dependence problem of AWG devices and the application of thermoelectric coolers in the field of optical communication.

Design, fabrication and characterization of arrayed waveguide grating devices based on different polymers

1 × 8 and 1 × 16 traditional/saddle arrayed waveguide grating (AWG) devices with different core layer materials applied in fiber Bragg grating (FBG) system were designed, fabricated and compared. We applied epoxy resin-type materials (SU-8) and polymethyl methacrylate (PMMA) as the core layer materials, and polymer polydimethylsiloxane (PDMS) was selected as the cladding material. We developed a chemical modification method in order to improve the film-forming properties of the core layer materials on the PDMS cladding layers. The dimensions of the fabricated AWGs with SU-8 core layers and PMMA core layers were smaller than 1.1 cm × 0.9 cm and 1.1 cm × 1.2 cm, respectively. According to the experimental results, the on-chip insertion losses of 1 × 8 and 1 × 16 SU-8 AWG devices were lower than those of PMMA AWG devices with the same type of arrayed waveguides and the number of input and output channels, with 2.83-dB and 2.26-dB lower values of the 1 × 8 and 1 × 16 SU-8 AWG devices, respectively.

Design, simulation and characterization of integrated photonic spectrographs for astronomy II: low-aberration Generation-II AWG devices with three stigmatic points.

In the second part of our series on integrated photonic spectrographs for astronomy, we present theoretical and experimental results on the design, simulation and characterization of custom-manufactured silica-on-silicon arrayed waveguide gratings (AWGs) constructed using the three-stigmatic-point method. We derive several mid-to-high resolution field-flattened AWG designs, targeting resolving powers of 11,000 - 35,000 in the astronomical H-band, by iterative computation of differential coefficients of the optical path function. We use numerical simulations to study the imaging properties of the designs in a wide wavelength range between 1500 nm and 1680 nm. We theoretically discuss the design-specific degradation of spectral resolving power at far-off-centre wavelengths and suggest possible solutions. In the experimental section, we provide characterization results of seven manufactured AWG devices of varying free spectral range and resolution. We obtain estimates on spectral resolving powers of up to 27,600 for polarized input at 1550 nm from measurements of the channel transmission bandwidth. Furthermore, we numerically predict expected resolving powers of up to 36,000 in the polarized mode and up to 24,000 in the unpolarized mode for direct continuous imaging of the spectrum.

Design, simulation and characterization of integrated photonic spectrographs for astronomy: generation-I AWG devices based on canonical layouts.

We present an experimental study on our first generation of custom-developed arrayed waveguide gratings (AWG) on a silica platform for spectroscopic applications in near-infrared astronomy. We provide a comprehensive description of the design, numerical simulation and characterization of several AWG devices aimed at spectral resolving powers of 15,000-60,000 in the astronomical H-band. We evaluate the spectral characteristics of the fabricated devices in terms of insertion loss and estimated spectral resolving power and compare the results with numerical simulations. We estimate resolving powers of up to 18,900 from the output channel 3-dB transmission bandwidth. Based on the first characterization results, we select two candidate AWGs for further processing by removal of the output waveguide array and polishing the output facet to optical quality with the goal of integration as the primary diffractive element in a cross-dispersed spectrograph. We further study the imaging properties of the processed AWGs with regards to spectral resolution in direct imaging mode, geometry-related defocus aberration, and polarization sensitivity of the spectral image. We identify phase error control, birefringence control, and aberration suppression as the three key areas of future research and development in the field of high-resolution AWG-based spectroscopy in astronomy.

AWG-based WDM ring networks: High-performance and low-cost system designs

Optical packet switching (OPS) ring networks are regarded as being promising solutions for future optical metropolitan area networks. In this paper, we propose novel arrayed-waveguide grating (AWG)-based wavelength division multiplexing (WDM) ring network systems that are aimed at achieving low-cost, scalable, and high-performance systems. By exploiting the cyclic routing properties and spatial wavelength reuse of a passive 2*2 AWG device, we redesign the ring network into a two-subring network, connected through the AWG device. The network is governed by a novel distributed medium access control (MAC) scheme, and we further derive a highly efficient and fair bandwidth allocation in accordance with a quota. A previously proposed experimental optical packet-switched WDM metro-ring network, called HOPSMAN, has shown to have exceptional performance among the OPS ring network studies. We show simulation and analytic results to demonstrate that our proposed system have achieved enhanced performance of the TT (tunable transmitter)-TR (tunable receiver)-based HOPSMAN by 1.5 times but have used only low-cost TT-FR (fixed-tuned receiver) or FT (fixed-tuned transmitter)-FR optical devices. Thus, the proposed networks achieve exceptional network throughput and also greatly reduce system costs.

硅光子阵列波导光栅器件研究进展

硅光子阵列波导光栅器件研究进展

Low-Loss Compact Silicon Nitride Arrayed Waveguide Gratings for Photonic Integrated Circuits

We report on low-loss, low-crosstalk, and compact arrayed waveguide gratings (AWGs) based on a 200-nm-thick-Si3 N4-core platform. High-resolution fabrication processes realized four types of Si3N4 AWG devices: 8 channel × 200 GHz, 16 channel × 100 GHz, 16 channel × 50 GHz, and 16 channel × 25 GHz AWGs. The insertion loss values of the four devices were 1.5 dB, 1.7 dB, 1.8 dB, and 2.7 dB; the corresponding crosstalk values were –24 dB, –21 dB, –20 dB, and –13 dB; footprints were 1.8 × 0.6 mm2, 2.2 × 0.7 mm2, 3.7 × 0.7 mm2, and 6.8 × 0.7 mm2, respectively.

Design of AWG Devices for All-Optical Time-Frequency Packing

We present the design guidelines for novel passive arrayed waveguide grating (AWG) devices to all-optically implement time-frequency packing techniques in orthogonal frequency division multiplexing (OFDM) systems. The proposed approach can increase the spectral efficiency in long-haul fiber links. We analyze the system performances, evaluating the maximum achievable information rate and spectral efficiency, and we found the optimal AWG layout to maximize the overall system capacity. We demonstrate, through simulations, that an overall 1.4 Tb/s transmission over 200 GHz bandwidth can be reached, using two polarizations, quadrature phase shift keying modulation, and digital feedback equalization.

Low-loss and low-crosstalk 8 × 8 silicon nanowire AWG routers fabricated with CMOS technology.

Low-loss and low-crosstalk 8 × 8 arrayed waveguide grating (AWG) routers based on silicon nanowire waveguides are reported. A comparative study of the measurement results of the 3.2 nm-channel-spacing AWGs with three different designs is performed to evaluate the effect of each optimal technique, showing that a comprehensive optimization technique is more effective to improve the device performance than a single optimization. Based on the comprehensive optimal design, we further design and experimentally demonstrate a new 8-channel 0.8 nm-channel-spacing silicon AWG router for dense wavelength division multiplexing (DWDM) application with 130 nm CMOS technology. The AWG router with a channel spacing of 3.2 nm (resp. 0.8 nm) exhibits low insertion loss of 2.32 dB (resp. 2.92 dB) and low crosstalk of -20.5~-24.5 dB (resp. -16.9~-17.8 dB). In addition, sophisticated measurements are presented including all-input transmission testing and high-speed WDM system demonstrations for these routers. The functionality of the Si nanowire AWG as a router is characterized and a good cyclic rotation property is demonstrated. Moreover, we test the optical eye diagrams and bit-error-rates (BER) of the de-multiplexed signal when the multi-wavelength high-speed signals are launched into the AWG routers in a system experiment. Clear optical eye diagrams and low power penalty from the system point of view are achieved thanks to the low crosstalk of the AWG devices.

Optical loss analysis in 13-channel SOI-based AWG for CWDM network

In this paper, we report the insertion loss and adjacent crosstalk for tapered and conventional configuration of double S-shaped design of arrayed waveguide grating (AWG) using 1.2 μm and 1.0 μm core width. The 13-channel AWG on silicon-on-insulator (SOI) was simulated using beam propagation method (BPM) at central wavelength of 1.49 μm, producing a transmission spectrum ranging from 1310–1620 nm. Tapered AWG for both core widths gave the lowest insertion loss of < 7 dB while only the AWG with the 1.2 μm core width produced the lowest crosstalk at < -19 dB compared to the other configurations. A 13-channel transmission spectrum of the AWG device has been produced which fits closely the standard ITU-T CWDM wavelength grid.

Athermal polarization-independent 49-channel UV curable all-polymer arrayed waveguide grating (AWG) multiplexer

In this paper, an athermal polarization-independent 49 channel arrayed-waveguide grating (AWG) multiplexer relying on a UV curable all-polymer approach was designed and fabricated by simple direct Ultraviolet photolithography process. The transmission properties of the AWG around the central wavelength of 1550.918nm with the wavelength spacing of 0.8nm were optimized by Matlab programming. By properly adjusting the positive coefficient of thermal expansion of the polymer substrate and the negative thermo-optic coefficient of the polymer waveguide, athermal and polarization-independent characteristics of AWG device were realized. The actual fiber–fiber insertion loss at each channel was from 5.51dB to 10.62dB, and the crosstalk of the 49 channels was less than −20dB. Both polarization drifts and temperature shifts of the AWG were 0.08nm and 0.03nmK−1, respectively. The new technique could be well suited for fabricating optical integrated circuits with excellent performances.

Analysis of fabrication results for 17 × 17 polymer arrayed waveguide grating multiplexers with flat spectral responses

Based on transmission theory, a 17 × 17 polymer arrayed waveguide grating (AWG) multiplexer parameter optimization is performed, and the influence of the fabrication results on the transmission characteristics are analyzed. In this paper, we mainly discuss three of the main errors in the fabrication of polymer AWG devices. One is δn1, which is caused by the tuning of the core refractive index n1, the second is δb, which results from the rotating-coating of the core thickness b, and the other is the non-ideal core cross-section, which is caused by steam redissolution. The effects of the above fabrication errors on the transmission characteristics of the AWG device are investigated, and compensation techniques are proposed. By comparing the theoretical simulation and experimental results, the shift in the transmission spectrum is reduced by 0.028 nm, the 3 dB bandwidth is increased by about 0.036 nm, the insertion loss is reduced by about 3 dB for the central channel and 4.5 dB for the edge channels, and the crosstalk is reduced by 1.5 dB.

Low-Polarization-Dependent Silica Waveguide Monolithically Integrated on SOI Photonic Platform

We developed a low-polarization-dependent silica- based waveguide, which can be monolithically integrated with a silicon (Si) waveguide device on a silicon-on-insulator (SOI) substrate. For the monolithic integration, silica-based materials must be deposited at low temperature in order not to damage Si waveguide devices. Due to this low-temperature fabrication method, however, the silica films exhibit high residual stress, resulting in high material birefringence. In order to compensate for this birefringence, we introduce a multi-layer core structure. First, we design the structure taking the monolithic integration with the Si waveguide devices into account. Then, the designed waveguides and arrayed-waveguide gratings (AWGs) are fabricated using low-temperature fabrication processes. Next, we experimentally confirm that the waveguide exhibits low waveguide birefringence. In addition, we monolithically integrate the AWG and Si waveguide devices.

Arrayed waveguide grating interrogator for fiber Bragg grating sensors: measurement and simulation

A fiber Bragg grating (FBG) interrogation system based on an intensity demodulation and demultiplexing of an arrayed waveguide grating (AWG) module is examined in detail. The influence of the spectral line shape of the FBG on the signal obtained from the AWG device is discussed by accomplishing the measurement and simulation of the system. The simulation of the system helps to create quickly and precisely calibration functions for nonsymmetric, tilted, or nonapodized FBGs. Experiments show that even small sidebands of nonapodized FBGs have strong influences on the signal resulted by an AWG device with a Gaussian profile.

Ultra Wide Wavelength Multiplexing/Demultiplexing Conventional Arrayed Waveguide Grating (AWG) Devices for Multi Band Applications

This paper has proposed new materials based conventional arrayed waveguide grating (AWG) devices such as pure silica glass (SiO 2), Lithium niobate (LiNbO 3), and gallium aluminum arsenide (Ga (1-x) Al (x) As) materials for multiplexing and demultiplexing applications in interval of 1.45 µm to 1.65 µm wavelength band, which including the short, conventional, long, and ultra long wavelength band. Moreover we have taken into account a comparison between these new materials within operating design parameters of conventional AWG devices such as diffraction order, length difference of adjacent waveguides, focal path length, free spectral range or region, maximum number of input/output wavelength channels, and maximum number of arrayed waveguides. As well as we have employed these materials based AWG to include Multi band applications under the effect of ambient temperature variations.

Low-loss Si_3N_4 arrayed-waveguide grating (de)multiplexer using nano-core optical waveguides

A 16-channel 200 GHz arrayed-waveguide grating (AWG) (de)-multiplexer is demonstrated experimentally by utilizing Si3N4 buried optical waveguides, which have 50 nm-thick Si3N4 cores and a 15 μm-thick SiO2 cladding. The structure with an ultra-thin core layer helps to reduce the scattering due to the sidewall roughness and consequently shows very low loss of about 0.4~0.8 dB/m. When using this type of optical waveguide for an AWG (de)multiplexer, there is no problem associated with gap refill using the upper-cladding material even when choosing a small (e.g., 1.0 μm) gap between adjacent arrayed waveguides, which helps to reduce the transition loss between the FPR (free-propagation region) and the arrayed waveguides. Therefore, the demonstrated AWG (de)multiplexer based on the present Si3N4 buried optical waveguides has a low on-chip loss. The fabricated AWG (de)multiplexer is characterized in two wavelength ranges around 1310 nm and 1550 nm, respectively. It shows that the crosstalk from adjacent and non-adjacent channels are about -30 dB, and -40 dB, respectively, at the wavelength range of 1310 nm. The Si3N4 AWG (de)multiplexer has a temperature dependence of about 0.011 nm/°C, which is close to that of a pure SiO2 AWG device.

Compact Arrayed Waveguide Grating Devices Based on Small SU-8 Strip Waveguides

Compact 48 × 48 and 23 × 23 arrayed waveguide grating (AWG) devices are realized by using SU-8 strip waveguides fabricated with the process of direct ultraviolet (UV) photolithography. The demonstrated 48-channel and 23-channel AWG devices operating around 1550 nm have a channel spacing of 0.8 nm (100 GHz) and 3.2 nm (400 GHz), respectively. Due to the high index-contrast of the SU-8 strip waveguide, the fabricated AWG has a very compact size of only about 0.22 × 0.47 cm2. For the fabricated 100 GHz-spaced AWG, the crosstalk between adjacent channels is less than -15 dB, and the polarization-dependent wavelength is about 0.72 nm (@1543.5 nm). The fabricated 400 GHz-spaced AWG device exhibits a crosstalk of less than -20 dB, a polarization-dependent wavelength of 0.02 nm (@1559.6 nm). Finally the temperature tenability of the present AWG device is also characterized. A 12 nm tuning range is observed as the temperature changes from 25°C to 115°C.

Design and fabrication of Poly(dimethylsiloxane) arrayed waveguide grating

We have designed, fabricated and characterized poly(dimethylsiloxane) (PDMS) arrayed waveguide grating (AWG) with four-channel output for operation in the visible light wavelength range. The PDMS AWG was realized based on the single-mode PDMS rib waveguide. The device was designed for 1 nm channel spacing with the wavelength ranging from 639 to 644 nm. The measured insertion loss is 11.4 dB at the peak transmission spectrum and the adjacent crosstalk is less than -16 dB. The AWG device occupies an area of 7.5 × 15 mm(2). PDMS AWG has the potential for integration with microfluidics in a monolithic PDMS lab-on-a-chip device for visible light spectroscopy applications.

Fabrication of 17 × 17 polymer/Si arrayed waveguide grating with flat spectral response using steam-redissolution technique

Arrayed waveguide grating (AWG) is a key device in the wavelength-division multiplexing (WDM) system, and the flat spectral response of the AWG device is required. In this paper, the RIE process has been improved. By using the steam-redissolution technique, the insertion loss and the crosstalk have been reduced. Experimental results show that the central wavelength is 1550.86 nm, the channel spectral response flatness is about 1.5 dB, 3-dB bandwidth is about 0.478 nm, insertion loss is 10.5 dB, and crosstalk is about −22 dB. The insertion loss of an AWG device is reduced by about 3 dB for the central channel and 4.5 dB for the edge channels, and the crosstalk is reduced by 2.5 dB after the steam- redissolution.