Silicon polarization independent microring resonator-based optical tunable filter circuit with fiber assembly

Demonstration of polarization-insensitive optical filters on silicon photonics platform

We experimentally demonstrate a polarization-insensitive optical filter (PIOF) using polarization rotator-splitters (PRSs) and microring resonators (MRRs) on the silicon-on-insulator (SOI) platform with complementary metal-oxide-semiconductor (CMOS) compatible fabrication process. The PRS consists of a tapered-rib waveguide and an asymmetrical directional coupler (ADC), which realize the polarization rotation and splitting, to ensure the connected MRRs-based optical filter operating at one desired polarization when light with different polarizations are launched into the device. The measured results show that the optical transmission spectra of the device are identical for TE and TM polarization input. The box-like filtering spectra are also achieved with a 3-dB bandwidth of ∼0.15 nm and a high extinction ratio (ER) over 30 dB.

Low-loss and ultra-broadband silicon nitride angled MMI polarization splitter/combiner

The property of self-imaging combined with the polarization birefringence of the angled multimode waveguide is used to design a silicon nitride (SiN) polarization splitter (PS) at λ ∼ 1550 nm. The demonstrated PS on a 450 nm thick SiN device layer (with 2.5 µm cladding oxide) has a footprint of 80 µm×13 µm and exhibits nearly wavelength independent performance over the C+L bands. Also, the device can be configured as a polarization combiner (PC) in reverse direction with similar bandwidth and performance. The measured crosstalk (CT) and insertion loss (IL) are respectively <-18 dB (<-20 dB) and ∼0.7 dB (∼0.8 dB) for TE (TM) polarization over the measurement wavelength range of 1525 nm ≤λ ≤ 1625 nm. The measured device parameter variations suggest some tolerance to fabrication variations. Such a device is a good candidate for a photonics integrated chip (PIC) foundry-compatible, SiN PS.

Photoinduced Tunable and Reconfigurable Electronic and Photonic Devices Using a Silk-Based Diffractive Optics Platform

A remarkable feature of modern electronic and photonic devices is the ability to maintain their geometric and physical properties in various circumstances for practical applications. However, there is an increasing demand for reconfigurable devices and systems that can be triggered or switched by external stimuli to change geometric, physical, and/or biochemical properties to meet specific requirements such as compact, lightweight, energy-efficient, and tunable features. Here, a set of phototunable and photoreconfigurable electronic and photonic devices composed of reconfigurable arithmetic circuits and programmable coding metamaterials at terahertz frequencies, empowered by a diffractive optics platform using naturally extracted silk proteins, is reported. These protein-based diffract optics are precisely manufactured into special microstructures for phase modulation of incident light and can be programmed to degrade at controlled rates. This allows spatial and temporal transformation of the incident light into desired intensity profiles to modulate the electrical properties of multiple photosensitive elements/components within the device simultaneously or discretely. Thus, the optoelectronic functionality of fabricated devices can be tailored to specific applications. Therefore, the approach makes it possible to efficiently fabricate tunable, reconfigurable transient electronic and photonic devices and systems.

Compact multimode waveguide based temperature-insensitive Mach-Zehnder interferometer

A novel multimode waveguide based Mach-Zehnder interferometer (MZI) is demonstrated on an SOI platform with the properties of compact footprint and temperature-insensitive operation. The device can achieve a thermal dependence around 13pm/°C in a wavelength range of 40nm. Owing to the utilization of one single straight multimode waveguide, the device is naturally immune to local temperature distributions. The measured results exhibit transmissions with an extinction ratio better than 8dB and a minimum insertion loss lower than 0.31dB over the wavelength range of 1545nm-1585nm. Moreover, the proposed device is compatible with CMOS process.

Narrow-band, polarization-independent, transmission filter in a silicon-on-insulator strip waveguide

We report on a narrow-band, polarization-independent, transmission filter using phase-shifted, polarization-rotating Bragg gratings (PRBGs) in a silicon-on-insulator strip waveguide. In our device, phase-shifted PRBGs provide narrow transmission peaks for the transverse electric (TE) and transverse magnetic (TM) modes, both at the same wavelength. We present results for a 330.6 μm long device that has transmission peaks centered at 1556.36 nm, 3 dB bandwidths of 0.26 nm, and extinction ratios of 19 dB for both TE and TM modes. We also integrated a heater onto our device and obtained a wavelength tuning efficiency of 0.028 nm/mW for both TE and TM modes.

Photoconductive effect on p-i-p micro-heaters integrated in silicon microring resonators

We study the photoconductive effect of a p-i-p micro-heater integrated in a microring resonator. Due to the surface state absorption (SSA) and two photon absorption (TPA) of optical wave around 1550 nm, free carriers are generated in the silicon waveguide, leading to the modulation of silicon conductivity and thus the current flowing through it. The current-voltage (I-V) response of the p-i-p diode is dependent on the bias voltage and can be divided into ohmic-law regime and space-charge-limited regime. The resonance peak current is more sensitive to optical power in the ohmic-law regime. Such a phenomenon can also be utilized to monitor the optical power in the waveguide.

CMOS-compatible temperature-independent tunable silicon optical lattice filters

We present a CMOS-compatible athermal tunable silicon optical lattice filter composed of 10 cascaded 2 × 2 asymmetric Mach-Zehnder interferometers. Active tuning experiments show that the filter central wavelength can be red-/blue-shifted by 13.1/21.3 nm with power consumption of 77/96 mW on top/bottom arms. Temperature shift measurements show that the thermal-sensitivity of the filter central wavelength before active tuning is as low as -1.465 pm/°C. The thermal-sensitivity is varied within 26.5 pm/°C to -27.1 pm/°C when the filter central wavelength is tuned in the wavelength range of 1534 nm to 1551 nm. We use the transfer matrix method to theoretically model the lattice filter and its thermal-sensitivity before and after tuning is analyzed and discussed.

Polarization splitter using horizontal slot waveguide

In this paper a compact and efficient polarization splitter using horizontal slotted waveguides is presented. The splitter is designed by finite-difference-time-domain simulation and realized experimentally. The splitter is built by using a direction coupler consisting of two horizontal slotted waveguides and achieves a high extinction ratio of 14.1 and 16.8 dB for cross and through ports. The optimal coupling length is found to be 15 µm. The device exhibits a good response of extinction ratio across C + L broadband. The splitter obtained is readily used for a polarization diversity circuit, particularly for platforms with horizontal slot waveguides.