Tunable Photonic Research Articles

Optimization of a Tunable Photonic Crystal Filter for Coarse Wavelength Division Multiplexing

Optimization of a Tunable Photonic Crystal Filter for Coarse Wavelength Division Multiplexing

Communications: PhotonicsViews 6/2019

PhotonicsViewsVolume 16, Issue 6 p. 12-15 CommunicationsFree Access Communications: PhotonicsViews 6/2019 First published: 14 November 2019 https://doi.org/10.1002/phvs.201970604AboutPDF ToolsExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat Reference: X. Ji et al.: On-chip Tunable Photonic Delay Line, APL Photonics, online September 17, 2019; DOI: 10.1063/1.5111164 D. A. Walker et al.: Rapid, large-volume, thermally controlled 3D printing using a mobile liquid interface, Science 366, 360 (2019); DOI: 10.1126/science.aax1562 Volume16, Issue6December 2019/January 2020Pages 12-15 ReferencesRelatedInformation

Symmetric Continuously Tunable Photonic Band Gaps in Blue-Phase Liquid Crystals Switched by an Alternating Current Field.

Symmetric continuously tunable three-dimensional (3D) liquid photonic crystals have been investigated using self-organized blue-phase liquid crystal films. The photonic band gap in the overall visible spectrum can be tuned continuously, reversibly, and rapidly as the applied electric field changes. After driven by the applied field, four-time enhancement of the reflectivity results in more vivid reflection colors. A lasing emission of tuning working wavelength has been demonstrated by using the dye-doped blue-phase liquid crystal film. With the advantages of fast response speed, no alignment layer, large-scale electrically shift of the photonic band gap, and macro optical isotropy, this self-assembled soft material has many potential applications in high-performance reflective full-color display, 3D tunable lasers, and nonlinear optics.

Acid mediated tunability of stimulated laser emission from dye doped chiral microdroplets

In the last decade, the possibility to use liquid crystal droplets as optical micro-cavities and lasers has attracted much attention since it paves the way for many applications in the field of sensors or tunable photonics. Several techniques can be used to obtain small micro-resonators as, for example, dispersing a cholesteric liquid crystal inside an immiscible isotropic fluid to create an emulsion. Since liquid crystals are extremely sensitive to external factors as temperature or external fields, laser tuning can be easily achieved. Here, we report on the possibility to tune the laser emission from dye doped cholesteric liquid crystals microdroplets dispersed in a glycerol matrix in presence of nitric acid molecules in the emulsion. Using a fluorescent dye with pH dependent optical properties, the emitted laser wavelength can be tuned in a range of 60 nm. This effect could find applications for the development of spectroscopy based sensors.

Freely Tunable Dual-Passband Microwave Photonic Filter Based on Phase-to-Intensity Modulation Conversion by Stimulated Brillouin Scattering

An approach to achieving a highly selective and stable microwave photonic filter (MPF) with two passbands independently tunable is presented. The dual-passband MPF is realized based on phase-to-intensity modulation conversion by stimulated Brillouin scattering. In the proposed scheme, a freely tunable two-tone pump is generated by passing the optical carrier through two cascaded dual-parallel Mach-Zehnder modulators (DPMZMs), with one acting as a frequency shifter with assistance of an electrical 90° hybrid and the other one working at carrier-suppressed double-sideband modulation mode to generate two-tone pump. The two passband locations of the MPF can be freely set by adjusting the frequencies of the two single-tone signals applied to the two DPMZMs. In the experiment, a dual-passband MPF with flexible passband tunability and shape-invariant tuning is demonstrated in the frequency range of 0-9.644 GHz, where the out-of-band rejection ratio and the 3-dB bandwidth of the passbands are measured to be larger than 25 dB and smaller than 55 MHz, respectively. The proposed MPF scheme also has the ability to tailor the shape and the width of the two passbands, which is a promising solution to achieve a freely programable dual-passband MPF.

基于啁啾光纤布拉格光栅的可调谐双通带微波光子滤波器

基于啁啾光纤布拉格光栅的可调谐双通带微波光子滤波器

Generation of Widely Tunable Narrow-Linewidth Photonic Microwave Signals Based on an Optoelectronic Oscillator Using an Optically Injected Semiconductor Laser as the Active Tunable Microwave Photonic Filter

In this work, a novel optoelectronic oscillator (OEO) structure is proposed for generating widely tunable photonic microwave. In this structure, an optical injection semiconductor laser (OISL) functions as an active tunable microwave photonic filter (MPF). Through controlling the injection power and frequency detuning, the OISL is driven into period-one dynamics whose oscillation frequency can be widely tuned from 10.43 to 65.82 GHz. As a result, the OISL can be regarded as a widely tunable active MPF. By introducing an optical feedback loop, the filtered bandwidth of the widely tunable active MPF can be further reduced. Taking the OISL under optical feedback as a widely tunable narrow-bandwidth MPF and a seeding laser source to establish an OEO structure, widely tunable narrow-linewidth photonic microwave can be generated. The experimental results demonstrate that widely tunable photonic microwaves ranging from 10.43 to 39.10 GHz with linewidths below 0.1 MHz and phase variances below 10−2 (rad2) can be achieved.

Microwave Photonic Image-Reject Mixer Based on a Tunable Microwave Photonic Filter With High Rejection

In a heterodyne receiver, the image can interfere with the desired signal and must be eliminated at the mixing stage. This paper presents a flexible microwave photonic image-reject mixer based on a widely tunable microwave photonic filter (MPF), which is used to select the desired signal and suppress the image. The MPF is realized by using stimulated Brillouin scattering, which offers significant advantages of wideband tunability, high selectivity, and large image rejection. In this work, a theoretical model is established to describe the operation principle of the proposed mixer at first. Then, in the experiment, a 7.8-GHz radio frequency (RF) signal is successfully down-converted to an intermediate frequency signal between 0.2 and 1.5 GHz, with an image rejection of larger than 40 dB. Additionally, when the RF frequency is tuned from 1.8 to 19.8 GHz, the image rejection remains above 40 dB.

Stable and Compact Dual-Loop Optoelectronic Oscillator Using Self-Polarization-Stabilization Technique and Multicore Fiber

We experimentally demonstrate a stable and compact dual-loop optoelectronic oscillator (OEO) using multicore fiber and self-polarization-stabilization technique. Two fiber cavities using two standard single mode fibers with different length in traditional dual-loop OEOs are replaced by only one multicore fiber where several cores are linked together to form the short and the long cavity simultaneously. Thanks to this fiber-integrated medium, the OEO relative stability is enhanced and the required cavity length is decreased. To avoid the influence from unstable polarization states of optical signals in these two fiber cavities, a self-polarization-stabilization technique is proposed. Therefore, no additional polarization controller and polarization maintaining fiber are required, contributing to further shorter fiber length in cavities and more compact structure. Moreover, the frequency and power stability of the generated RF signal in OEO is improved a lot compared with the traditional dual-loop OEO using the polarization division multiplexing technique. The experimental results show that the frequency and power drift of the generated RF signal with frequency of 7.8 GHz are within 0.59 ppm and 0.44 dB during 1 h, respectively. Furthermore, by introducing a tunable microwave photonics filter, a frequency tunable OEO is achieved. The experimental results show that the frequency of the generated RF signal could be tuned from 3.5 to 17.1 GHz, the phase noise performance at 10 kHz frequency offset is around −100 dBc/Hz in whole frequency range, and the side mode suppression ratio is 61 dB.

Tunable microwave photonics filter with dual pass-band based on PM-FBG and PS-FBG

In this paper, a dual pass-band microwave photonics filter with simple, commercial structure is proposed and demonstrated. The key devices are the specially designed polarization maintaining fiber Bragg grating and the phase shift fiber Bragg grating. They are employed to extract out two orthogonally polarized sidebands and remove the undesired sideband, respectively. The simulation results show that without any extra operations or electrical processing, the dual pass-band can be achieved with the two central frequencies of 3.5 GHz and 8 GHz when the frequency spacing between the two orthogonally polarized sidebands is 12 GHz, their 3-dB bandwidth are about 500 MHz. The central frequencies of the two pass-bands can be simply tuned by adjusting the frequency spacing in a range of 4 GHz. In addition, the spurious free dynamic ranges for the two pass-bands are 75.71 dB Hz2/3 and 70.17 dB Hz2/3 respectively. Finally, a brief experiment is also carried out to demonstrate the feasibility.

Flexible All‐Solid‐State Electrically Tunable Photonic Crystals

AbstractElectrically tunable photonic crystals (ETPCs) are promising intelligent materials because of their precise and easy control, fast response time, and convenient implementation. However, the previously reported ETPCs require specific liquid cells that contain solvent, electrolytes, or liquid crystals. These features result in a long switching time, large hysteresis, long and complex fabrication process, and unstable operation with a short lifetime. Here, to address these issues, a new approach of ETPCs, that is, flexible all‐solid‐state ETPCs, is proposed through chemically induced polymer swelling and lattice control in photonic crystals using dielectric elastomer actuators (DEAs). The all‐solid‐state ETPCs show a wide range of color changes from red to blue‐green and long‐term stable operation with low hysteresis. The DEA coated with transparent compliant electrodes stretches the chemically swollen colloidal crystal‐polydimethylsiloxane composite (redshift) under an applied electric field; the swollen interlattice distance in the colloidal crystals decreases with the electrically induced stretching, causing a blueshift in the color. The conformable color change of the ETPCs on a 3D structure is successfully demonstrated owing to their unique flexibility by covering 3D surfaces with the developed ETPCs. The proposed flexible all‐solid‐state ETPCs are expected to be used as artificial camouflage skins in the future.

Tunable SNAP microresonators via internal ohmic heating

We demonstrate a thermally tunable surface nanoscale axial photonics (SNAP) platform. Stable tuning is achieved by heating a SNAP structure fabricated on the surface of a silica capillary with a metal wire positioned inside. Heating a SNAP microresonator with a uniform wire introduces uniform variation of its effective radius which results in constant shift of its resonance wavelengths. Heating with a nonuniform wire allows local nanoscale variation of the capillary effective radius, which enables differential tuning of the spectrum of SNAP structures, as well as the creation of temporary SNAP microresonators that exist only when current is applied. As an example, we fabricate two bottle microresonators coupled to each other and demonstrate differential tuning of their resonance wavelengths into and out of degeneracy with precision better than 0.2pm. The developed approach is beneficial for ultra-precise fabrication of tunable ultralow loss parity-time symmetric, optomechanical, and cavity quantum electrodynamics (QED) devices.

Tunable Single-Passband Microwave Photonic Filter Based on Integrated Optical Double Notch Filter

A novel-integration-based technique employing a cascaded pair of microring resonators on silicon-on-insulator platform that can achieve a tunable single-passband microwave photonic filter with improved shape factor and extinction ratio is presented. It is based on an integrated optical double notch filter using a cascaded pair of nonidentical microring resonators, in conjunction with optical phase modulation. This results in minimal net phase being introduced by the overall filter at radio frequencies falling outside the region of the notch stopband, thus enabling nearly full antiphase cancellation of the modulation sidebands, which results in the achievement of an improved filter shape factor and extinction ratio. Additionally, it features a bandwidth that is directly determined by the difference between the bandwidths of the two optical notch filters, rather than by their absolute individual bandwidths. Experimental results have verified the concept, and have demonstrated a single-passband filter having tuning range of 6–17 GHz, a shape factor of 1.78, shape-invariant tuning, and a good out-of-band suppression ratio of approximately 20 dB throughout the entire tuning range.

A Continuously Tunable Sub-Gigahertz Microwave Photonic Bandpass Filter Based on an Ultra-High-Q Silicon Microring Resonator

Microwave photonic filter (MPF) is one of the key fundamental subsystems in microwave photonics, and it shows great potentiality in numbers of applications such as optoelectronic oscillator, microwave frequency measurement, and so forth. A narrowband bandpass MPF is highly desirable with its high selectivity in microwave photonic applications. However, a resonator with a high quality factor (>106) is very difficult to fabricate on the mature silicon photonics platform without optimization, thus restraining the applications of the MPF. In this paper, we propose and experimentally demonstrate a tunable sub-gigahertz bandwidth MPF based on an ultrahigh quality factor silicon microring resonator. Most performance aspects of the MPF are well-balanced. A full width at half-maximum bandwidth of 170 MHz is achieved thanks to the ultrahigh total quality factor as 1.14 × 106 of the microring resonator, and the average waveguide loss and the intrinsic Q factor of the microring resonator are calculated as 0.25 dB/cm and 2.67 × 106, respectively. The corresponding rejection ratio of the bandpass filter is 26.5 dB. Besides, the central frequency of the filter could be continuously tuned from 2.0 to 18.4 GHz with a microheater fabricated upon the microring, and a 16.4 GHz tuning range is achieved with the maximum power consumption of 14.4 mW. The device area is ∼0.05 mm2.

Wireless Data Transmission at Terahertz Carrier Waves Generated from a Hybrid InP-Polymer Dual Tunable DBR Laser Photonic Integrated Circuit

We report for the first time the successful wavelength stabilization of two hybrid integrated InP/Polymer DBR lasers through optical injection. The two InP/Polymer DBR lasers are integrated into a photonic integrated circuit, providing an ideal source for millimeter and Terahertz wave generation by optical heterodyne technique. These lasers offer the widest tuning range of the carrier wave demonstrated to date up into the Terahertz range, about 20 nm (2.5 THz) on a single photonic integrated circuit. We demonstrate the application of this source to generate a carrier wave at 330 GHz to establish a wireless data transmission link at a data rate up to 18 Gbit/s. Using a coherent detection scheme we increase the sensitivity by more than 10 dB over direct detection.

A Multichannel Phase Tunable Microwave Photonic Mixer With High Conversion Gain and Elimination of Dispersion-Induced Power Fading

A microwave photonic system that can realize frequency up- and down-conversion, multichannel phase shift, high conversion gain, and elimination of dispersion-induced power fading is proposed and experimentally demonstrated. The scheme is based on an integrated dual-polarization quadrature phase shift keying modulator that contains two dual parallel Mach–Zehnder modulators (X-DPMZM and Y-DPMZM). The X-DPMZM implements dual side band carrier suppression (DSB-CS) modulation of radio frequency signal, and the Y-DPMZM implements frequency shift of an optical carrier. They are combined in orthogonal polarizations to implement frequency up- and down-conversion. The polarization multiplexed signal will go through polarization controllers and polarizers to implement multichannel phase shift. In the experiment, the phase shift can be tuned independently over 360° in each channel. By suppressing the optical carrier, the conversion gain and LO isolation are improved by 20.5 dB and 51.26 dB, respectively, compared with conventional dual side band modulation scheme. In addition, the proposed scheme can achieve a spurious-free dynamic range (SFDR) of 103.6 dB·Hz2/3.

Temperature-tunable lasing from dye-doped chiral microdroplets encapsulated in a thin polymeric film.

In the last decade, much interest has grown around the possibility to use liquid-crystal droplets as optical microcavities and lasers. In particular, 3D laser emission from dye-doped cholesteric liquid crystals confined inside microdroplets paves the way for many applications in the field of sensors or tunable photonics. Several techniques can be used to obtain small microresonators as, for example, dispersing a liquid crystal inside an immiscible isotropic fluid to create an emulsion. Recently, the possibility to obtain a thin free-standing film starting from an emulsion having a mixture of water and polyvinyl alcohol as isotropic matrix has been reported. After the water evaporation, a polymeric film in which the microdroplets are encapsulated has been obtained. Bragg-type laser emission has been recorded from the emulsion as well as from the thin film. Here, we report on the possibility to tune the laser emission as a function of temperature. Using a chiral dopant with temperature dependent solubility, the emitted laser wavelength can be tuned in a range of 40 nm by a temperature variation of 18 °C. The proposed device can have applications in the field of sensors and for the development of anti-counterfeiting labels.

A Tunable Single Passband Microwave Photonic Filter of Overcoming Fiber Dispersion Induced Amplitude Fading

A tunable single passband microwave photonic filter (MPF) of overcoming fiber dispersion induced amplitude fading of the microwave passband is proposed and demonstrated. The passband amplitude of the MPF can be kept invariant for different central frequencies. The scheme is realized based on a dual-drive Mach–Zehnder modulator (DDMZM) and a broadband optical source sliced by a delay interferometer. The DDMZM is single-electrode driven and the microwave signal is modulated onto the optical carrier with simultaneous phase and intensity modulation formats. The ratio of the two modulation formats can be controlled by adjusting the bias of DDMZM to compensate the dispersion-induced amplitude fading at any passband of the MPF. In the experiment, the proposed MPF can be tuned between 0 and 30 GHz and the rejection ratio exceeds 30 dB.

Tunable Dual-Passband Microwave Photonic Filter Based on Stimulated Brillouin Scattering

A novel ultra-narrow dual-passband microwave photonic filter (MPF) with wide tunability based on stimulated Brillouin scattering (SBS) is presented. The proposed dual-passband MPF is implemented via the usage of carrier suppressed modulation of an electrooptic modulator (EOM). The passband separation of the dual-passband filter is determined by the oscillation radio frequency (RF) that is applied onto the EOM, where the frequency change of the RF oscillator results in two times the bandpass frequency shift with a central frequency that is symmetric with respect to the SBS frequency shift. A complete theoretical model based on the combined effects of the Brillouin gain and loss in a dual-wavelength Brillouin pump structure is presented to characterize the filter RF responses. Experimental results show a widely tunable dual-passband MPF that has an ultra-narrow bandwidth of 20.1MHz with over 35 dB out-of-band rejection ratio and a 20-3-dB bandwidth shape factor of 2.5.

Microstructured optical fiber for multichannel sensing based on Fano resonance of the whispering gallery modes.

We present the design and theoretical demonstration of a microstructured optical fiber (MOF) for multichannel sensing applications based on the Fano resonance among the different whispering-gallery modes (WGMs) propagating in the MOF. The proposed MOF consists of a number of capillary channels with different diameters inside a tubular frame. When the phases of the WGMs in the capillary channels and the frame are matched, the Fano resonance will occur and the resonant peaks can be observed in the output spectrum of the tubular frame resonator. Sensing signals from the individual channels can be detected by measuring the central wavelengths of the corresponding Fano resonant peaks. To demonstrate the practicality, we study a dual-channel MOF for bio-sensing applications, i.e., detecting the refractive index variation in biological samples. In the analysis, we have shown that channel 1 and 2 achieve a sensitivity of 29.0557 nm/RIU (refractive index unit) and 22.9160 nm/RIU in the TE mode; and 16.0694 nm/RIU and 13.3181 nm/RIU in the TM mode respectively, when the refractive index of the biological samples varies between 1.330 and 1.345. The new MOF can be a compact, flexible, and low-cost solution for a variety of applications including multichannel bio/chemical sensing, multi-microcavity laser, and tunable photonics devices.