At CPPICS, we are dedicated to advancing light-based technologies, and our state-of-the-art research facilities and design tools, including Ansys Lumerical, Cadence Photonics, COMSOL, TCAD Synopsys, and Klayout, empower researchers and scholars to explore the vast potential of photonic integrated circuits. Our in-house fabrication capabilities include Electron Beam lithography, Deep UV, Mask Writer, Chemical Mechanical Polishing, P & N Diffusion, and more. For device characterization, we utilize manual and automatic probe stations, Lightwave Component Analyzers, and Optical Complex Spectrum Analysers alongside other cutting-edge tools.
As part of our commitment to innovation, CPPICS is actively developing indigenous PIC design rules and hardware infrastructure for precision packaging in in-house system-level applications and field trials. To strengthen this mission, we have partnered with Si2 Microsystems, Bangalore, for joint development of packaging rules, technology transfer, and supporting futuristic start-up businesses.

• Design Tools
• Process Equipment
• Characterization Tools
• Packaging & Testing

Lumerical is a high-performance photonic simulation software. It houses various physical solvers for electromagnetics, heat transfer, charge distribution etc. adopting different numerical methods like Finite Difference, Finite Element, Finite Difference Time Domain and so on. We use it to design and simulate various passive and active photonic devices like waveguides, directional couplers, MMIs, DBR, phase shifters etc. and also photonic circuits.

COMSOL offers an extensive range of scientific models, encompassing acoustics, electromagnetics, chemical reactions, fluid dynamics, heat transfer, and more. Our focus lies in harnessing the power of this software for two critical domains: heat transfer physics and electromagnetics. In the realm of heat transfer physics, we employ COMSOL to model thermo-optic phase shifters and photonic waveguides. This enables us to explore the behaviour of light and heat interactions, paving the way for cutting-edge advancements in photonics technologies.
In the field of electromagnetics, COMSOL becomes a powerful tool in our pursuit to understand and mitigate crosstalk in large-scale photonic integrated circuits. By simulating and analyzing electromagnetic phenomena, we gain invaluable insights that drive the development of high- performance photonic devices.

A PIC requires efficient electronic driver circuits to actively control the flow of light within the chip. Through Cadence's Electronic and Photonic Design Automation (EPDA) environment, we embark on a cost-effective journey of monolithic integration, combining electronic and photonic circuits seamlessly. With the EPDA environment, we unlock the potential for parallel simulations of electronics and photonics circuits. Our focus lies in designing robust driver circuits for PICs, ensuring optimal performance and functionality. Additionally, we explore the co-integration of electronic drivers with integrated photonic devices like modulators, Photonic switches, and Quantum Key Distribution (QKD) components.
Through cutting-edge simulations and advanced design techniques, we pave the way for a transformative landscape of PICs, where the combination of electronics and photonics unlocks unprecedented possibilities.

Technology Computer-Aided Design (TCAD) is the utilization of computer simulations to advance and refine semiconductor process technologies and devices. Sentaurus is a suite of TCAD tools which simulates the fabrication, operation and reliability of semiconductor devices. The Sentaurus simulators use physical models to represent the wafer fabrication steps and device operation, thereby allowing the exploration and optimization of new semiconductor devices. It is an advanced multidimensional device simulator capable of simulating electrical, thermal, and optical characteristics of silicon-based and compound semiconductor devices.

Inductively Coupled Plasma Reactive Ion Etching (ICPRIE)

This process is used to etch the required area and thickness of the substrate to get desired devices.Oxford Plasmalab System 100 is the equipment available for this process with Cl2 + Br2.

ICPCVD

It’s the process of depositing different material such as silicon dioxide, silicon nitride on substrate. In Oxford Plasma Lab 100, the deposition process is usually carried out at low temperature i.e. less than 400 degrees.

Photolithography

It’s the process of transferring the desired device patterns onto the substrate/sample (Silicon and Silicon Nitride in our case) using light. The Mask Aligner tool MA6/BA6 from Suss Microtec, Germany is capable of giving a minimum feature size down to 1 µm along with user-friendly interface,Also, the DUV lithography tool, similar to above model is available and capable of minimum feature size of 700nm.

Mask Writing

Photo masks contain the patterns that get transferred to substrate during photolithography. DWL 66 from Heidelberg Instruments GmbH, Germany is the tool used for direct laser writing of photo masks which has capability to write feature size down to 1 µm.

E-Beam Lithography

The Raith 150TWO is an ultra-high resolution electron beam lithography (EBL) tool for nanoscale fabrication. The tool is capable of writing sub-10 nm features. Electron beam energy can be varied from 100 eV to 30 KeV. The system can handle a wide range of samples up to 8-inch wafers. This system has fixed beam moving stage (FBMS) and modulated beam moving stage (MBMS) exposures. It can handle 7-inch masks and perform automatic focus correction. We use the EBL system for the fabrication of photonic integrated circuits on silicon and silicon nitride platforms. In addition, it serves as an invaluable tool for mask writing for the photolithography processes.

Oxidation & Diffusion & Thin film Deposition

This 4-stack horizontal furnace system by SVCS has dedicated tubes, each for thermal oxidation, high temperature annealing, phosphorus and boron diffusion to get n and p-type doping respectively. The furnace tubes can withstand a maximum temperature of 1000°C. The temperature, pressure, process time, gas (Oxygen and purge Nitrogen) ratios and steamer rate (for wet oxidation) can be individually controlled. Loading is mechanical and the oxidation and annealing furnaces can handle processing of a total of 25 four inch wafers each.

Metallization

It’s the process of depositing thin layer of metals on top of sample for getting contact pads and microheaters. Three types of equipment are available mainly for Thermal Evaporation (HPVT 305G Hydro Pneo Vac Technologies, India), E-beam Evaporation (BOC Edwards Auto 306 and Hind Hi Vac BC 300T), DC and RF Sputtering (Hind High Vac).

Dicing

It’s the method of separating individual die from each other on the wafer. The equipment used is Advanced Dicing Technology 7100-Provectvs.

Polishing

This process helps in removing the surface roughness and getting rid of contaminants or subsurface damages. The equipment used is Ultra Pol Ultra Tech Manufacturing Inc., USA.

Wire Bonding

It’s the process of making interconnects between the IC and the PCB or between multiple ICs. The equipment used is TPT HB10.

Chemical Mechanical Polishing

The CMP Tribo by Logitech is an industry-standard bench-top Chemical Mechanical Polishing (CMP) system. It handles wafer sizes of up to 4 inches with precision in achieving nanometer-level surface roughness and a dedicated pad conditioning carrier head. In our silicon photonic device fabrication process, we rely on the CMP Tribo for planarizing wafer-scale Silicon Nitride and Silicon-dioxide materials. This crucial step ensures the smooth and uniform surface necessary for the successful development of high-performance silicon photonic devices.

LPCVD

FirstNano Easy Tube 6000 comprises of a 4 stack horizontal chemical vapour deposition (CVD) system with a mechanical loading platform for each furnace tube. The temperature, pressure, process time and gas rates can be individually controlledby a computet running Labview. The system utilizes Nitrogen as the carrier gas and has Oxygen, Dicholorosilane and Ammonia as the feedstock, required for the different furnace tubes each dedicated foe Low Temperature Oxide (LTO), Silicon Nitride (SiN), Polysilicon deposition and Si Nano-rod formation respectively. For Integrated Photonics, we rely on high quality, optical grade SiN layer deposited using this system at low pressure and high temperature. The furnaces can go up to a maximum temperature of 900°C and the wafer boat can support processing of total of 25 four inch wafers simultaneously.

Upcoming Facilities

E-Beam Deposition System : Fully automatic stand alone Electron Beam evaporator system.

*** Mentioned Process Facilities are Available as Part of CPPICS and CNNP (Centre for NEMS and Nanophotonics) ,IIT Madras. ***

Ellipsometer

An ellipsometer is helpful for the characterization of thin films (in the order of nm) deposited/grown on top of a substrate. The Woollam Spectroscopic M-2000VI Ellipsometer provides the measurement spectrum over the range of 370-1690 nm (ultra-violet, visible and infra-red). The device can measure the characteristics for 580 wavelengths in the span of 2-5 seconds. The device can also characterize the deposited film for different incident angles, thus improving the measurement accuracy.

Confocal Microscope

The Olympus laser microscope OLS4000 is helpful in the nanometer level imaging and estimate the surface roughness. The non-contact surface profile measurement (using a low spot size laser source) is non-destructive and allows the accuracy to go to the sub-micron range.

Optical Spectrum Analyzer

APEX 2043B optical spectrum analyzer offers a wavelength resolution bandwidth of up to 0.04 pm to characterize optical devices. The resolution provided by the device is very beneficial, especially in the case of high Q (narrow bandwidth) micro-ring resonators, for Microwave and Quantum Photonics applications. The device also offers a tunable laser source over the wavelength range of 1520-1630 nm, with the capability to sweep the entire range in few seconds.

Grating Coupler Setup

The grating coupler setup helps to characterize the fabricated silicon photonic devices. It enables the launch and detection of the laser through the optical fibre with a 6 dB/facet coupling loss. The setup was designed and tested by our group of alumni here at IIT Madras. The launch angle into the on-chip device is 10 degree. The fibre alignment is done manually with the help of a microscope. The setup is isolated from any ambience disturbances through the vibration isolation system of the table.

Wave Shaper

Programmable Optical Wave Shaper (II-VI 1000A) provides a range of programmable optical filtering and switching options for photonics experiments. It has a Operating Wavelength Range of 1530 nm to 1565 nm. Two units are available in the lab.

Mode Lock Laser

Mode Lock Laser (Pritel FFL Series) produces pulses of light of extremely short duration, on the order of picoseconds. It has a Wavelength range of 1530 - 1565 nm and equiped with Pulse Repetition Rate (PRR) of 31.25 MHz, 62.5 MHz, 125 MHz, 250 MHz, 500 MHz, 1 GHz, 5 GHz, and 10 GHz with Internal RF Synthesizer.

Lightwave Component Analyzer

The The Lightwave Component Analyzer (LCA) interfaced with Performance Network Analyser (PNA) is used to measure the S-parameters of a microwave photonic link. The LCA comprises inbuilt laser source, intensity modulator and photodetector. The lab is equipped with two Keysight LCAs with the measurement capabilities up to 26.5 GHz and 50 GHz. The Spectrum Analyser inbuilt with the LCA helps to characterize several link parameters such as n^th order output and input intercept points (OIPn, IIPn), spurious free dynamic range (SFDRn) and noise figure.

Erbium Doped Fiber Amplifier

High Power Erbium Doped Fiber Amplifier amplifies (EDFA) the low input optical signal and gives high optical output power. We have one high power EDFA (Pritel) and one polarization maintaining EDFA (Pritel) with a wavelength range of 1535 nm to 1565 nm and saturated output power greater than 37 dBm.

Highly Coherent Laser Source

Highly Coherent Tunable Laser Source (Santec TSL-570) has equiped with a wavelength tuning range of 1480 nm to 1630 nm and max output power of +13 dBm.

Tunable Laser Source

A Tunable Laser Source (Apex AP3350A ) has equiped with a Two different module types are available: AP3350A and AP3352A, which covers C-band and L-band respectively. These tunable laser source modules can cover a wavelength range of 82 nm from 1526 nm to 1608 nm.

Probe Station

FormFactor High Precision Silicon Photonics Probe Station is used for a stable optical and electrical characterization of photonic integrated circuits. The equipment can handle 6-inch photonic wafers and is equipped to perform multi-channel DC probing (currently 16) and RF characterization up to 50 GHz.

Superconducting Nanowire Single Photon Detector

A near-infrared superconducting nanowire single-photon detector (SNSPD) system (Single Quantum Eos CS-8 channel and efficiency>80%) is being used for quantum photonics experimental studies.

RF Phase Noise Analyzer

The Holzworth phase noise analyser is used to test the quality of a given RF source by measuring its phase noise. We have the equipment to perform the measurements up to 26.5 GHz.

40 GHz Intensity Modulator & Phase Modulators

The modulators are the basic building blocks of any microwave photonic link. We have the Thorlabs intensity and phase modulators that can operate up to 40 GHz.
The drivers are essential for the active control of the bias conditions for an intensity modulator. The lab is equipped with two Thorlabs highly precise modulator drivers which can automatically bias the modulator in QUAD, PEAK and NULL operating conditions.

Arbitrary Waveform Generator

The Keysight Arbitrary waveform generator (AWG) provides complex signals at 128 GSa/s with 50Ghz analog bandwidth with 2 independent channels. AWG can be used to test modulators and photodetectors with different modulation formats such as PAM4, QPSK, etc. AWG can help in implementing different QKD schemes with its PRBS generator or by feeding the QRNG data to AWG to generate a custom waveform.

High-Resolution Real Time Oscilloscope

The Keysight Infiniium UXR Oscilloscope can sample signals at 256 GSa/s with 10-bit ADC with 50 GHz analog bandwidth in 2 channels. Along with the help of AWG, the Oscilloscope can be used to visualize different modulation formats applied to test modulators. It greatly helps in debugging optical systems such as QKD or optical communication.

High Speed Photodetector

A balanced photodetector is used in different types of optical measurements where we need to perform homodyne/heterodyne detection. Operating within the wavelength range of 1525 to 1570 nm, the FINISAR balanced photodetector offers a remarkable radio frequency (RF) bandwidth of 100 GHz. with optical power upto 10 mW at each input port. The device is being used in Quantum Random Number Generation (QRNG) experiments in our lab.

High Resolution Source Optical Analyzer

APEX2683A Optical Complex Spectrum Analyzer (OCSA) offers measurement of optical phase along with the power spectrum of signals with bandwidth resolution of 0.8pm, 0.16pm and 0.04 pm @ 100MHz, 20MHz and 5MHz. This device offers the phase measurements for the signals with repetitive rate of 20MHz to 900MHz for different modulation techniques over the wavelength range of 1520-1630 nm. This device has the sweep speed of 1.2nm/sec for the entire wavelength range. Furthermore, it can also display constellation, phase and intensity eye diagrams.

Upcoming Facilities

Fully Automated Probe Station: Used for Wafer level passive and active characterization of optical devices.

*** Mentioned Characterization Tools are Available as Part of CPPICS and IO Lab (Integrated Optoelectronics Lab) ,IIT Madras. ***

Photonic packaging is pivotal in integrating essential elements, such as a LASER source, fiber-chip coupling, photonic integrated circuits (PICs), and photodetectors. Notably, two robust vertical grating-coupling schemes, the V-Groove Array (VGA) and Quasi-Planar Coupling (QPC), are widely recognized for their exceptional optical alignment tolerances in fiber-chip coupling methods. To ensure a stable configuration of the PIC, we adopt an effective approach by placing the Thermo-Electric Cooler (TEC) and thermistor beneath it to facilitate efficient heat dissipation. Our power management involves using a programmable power supply with a printed circuit board (PCB) to drive essential components like the LASER, PICs, TEC, and thermistors. The interconnection between PICs and the PCB is achieved through precise wire bonding. With a specialized focus on VGA/QPC coupling in PICs and proficiency in efficient electrical packaging, including driver circuitry and wire bonding, we collaborated with Si2 Microsystems, Bangalore, India. Together, we completed both the electrical and optical packaging phases.