scholarly journals Sub-MHz spectral dip in a resonator-free twisted gain medium

2021 ◽  
Author(s):  
Neel Choksi ◽  
Yi Liu ◽  
Rojina Ghasemi ◽  
Li Qian
Keyword(s):  
Slow Light ◽  
Brillouin Scattering ◽  
High Sensitivity ◽  
Gain Medium ◽  
Spectral Features ◽  
New Paradigm ◽  
Microwave Photonic Filters ◽  
Spun Fiber ◽  
Brillouin Gain ◽  
Q Factors

Abstract Ultra-narrow optical spectral features have broad applications in spectroscopy, slow light, and sensing. Features approaching sub-MHz, or equivalently, Q-factors approaching 1 billion and beyond, are challenging to obtain in solid-state systems, ultimately limited by loss. We present a new paradigm to achieve tunable sub-MHz spectral features at room temperature without resonators. We exploit gain-enhanced polarization pulling in a twisted birefringent medium where polarization eigenmodes are frequency-dependent. Using Brillouin gain in a commercial spun fiber, we experimentally achieve a 0.72 MHz spectral dip, the narrowest backward Brillouin scattering feature ever reported. Further optimization can potentially reduce the linewidth to <0.1 MHz. Our approach is simple and broadly applicable, offering on-demand tunability and high sensitivity, opening a new paradigm for microwave photonic filters, slow light, and optical sensing.

scholarly journals Sub-MHz spectral dip in a resonator-free twistedgain medium

2021 ◽  
Author(s):  
Neel Choksi ◽  
Yi Liu ◽  
Rojina Ghasemi ◽  
Li Qian
Keyword(s):  
Room Temperature ◽  
Slow Light ◽  
Brillouin Scattering ◽  
High Sensitivity ◽  
Spectral Features ◽  
New Paradigm ◽  
Microwave Photonic Filters ◽  
Spun Fiber ◽  
Brillouin Gain ◽  
Q Factors

Abstract Ultra-narrow optical spectral features have broad applications in spectroscopy, slow light, and sensing. Features approaching sub-MHz, or equivalently, Q-factors approaching 1 billion and beyond, are challenging to obtain in solid-state systems, ultimately limited by loss. We present a new paradigm to achieve tunable sub-MHz spectral features at room temperature without resonators. We exploit gain-enhanced polarization pulling in a twisted birefringent medium where polarization eigenmodes are frequency-dependent. Using Brillouin gain in a commercial spun fiber, we experimentally achieve a 0.72 MHz spectral dip, the narrowest backward Brillouin scattering feature ever reported. Further optimization can potentially reduce the linewidth to <0.1 MHz. Our approach is simple and broadly applicable, offering on-demand tunability and high sensitivity, opening a new paradigm for microwave photonic filters, slow light, and optical sensing.

scholarly journals Resonator-free sub-MHz spectral dip in a twisted gain medium

2021 ◽  
Author(s):  
Neel Choksi ◽  
Yi Liu ◽  
Rojina Ghasemi ◽  
Li Qian
Keyword(s):  
Slow Light ◽  
Spectral Feature ◽  
Microwave Photonics ◽  
Gain Medium ◽  
Signal Attenuation ◽  
Pump Frequency ◽  
Resonant Structures ◽  
Dependent Polarization ◽  
Brillouin Gain ◽  
Spectral Location

Abstract Ultra-narrow spectral features are desirable for a broad range of applications, from precision spectroscopy to atomic clocks to slow-light and microwave photonics, and are conventionally realized using either ultrahigh-Q resonant structures or atomic resonances. Ultrahigh-Q structure often involves microfabrication, and suffers from loss mechanisms and manufacturing variations that cannot be easily compensated, whereas atomic resonances suffer from signal attenuation and tunability is a challenge. Here, we propose an entirely new way to achieve a sub-MHz and tunable spectral feature in a resonator-free gain medium, exploiting polarization pulling in a medium with frequency dependent polarization eigenmodes. To demonstrate a specific realization, we use Brillouin gain in a commercial spun fiber and experimentally achieve a 0.72 MHz spectral dip, which is to our knowledge, the narrowest spectral Brillouin feature ever reported. Furthermore, the simulation shows that the dip linewidth can be reduced to <0.1MHz, equivalent to a Q of almost 2 billion, by optimizing the birefringence and spun rate of the fiber. We also show that the linewidth, depth, and spectral location of this dip are all tunable on demand by controlling the pump frequency, pump power, and the input polarization of the signal. Its simplicity in implementation and broad applicability, its ultra-narrow linewidth, its tunability makes this approach extremely attractive for applications such as high precision metrology and microwave photonics.

scholarly journals Towards lab-on-chip ultrasensitive ethanol detection using photonic crystal waveguide operating in the mid infrared

Nanophotonics ◽  
2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Ali Rostamian ◽  
Ehsan Madadi-Kandjani ◽  
Hamed Dalir ◽  
Volker J. Sorger ◽  
Ray T. Chen
Keyword(s):  
Photonic Crystal ◽  
Slow Light ◽  
High Sensitivity ◽  
Guided Wave ◽  
Silicon On Insulator ◽  
Group Index ◽  
Photonic Crystal Waveguide ◽  
Mid Infrared ◽  
Lab On Chip ◽  
On Chip

Abstract Thanks to the unique molecular fingerprints in the mid-infrared spectral region, absorption spectroscopy in this regime has attracted widespread attention in recent years. Contrary to commercially available infrared spectrometers, which are limited by being bulky and cost-intensive, laboratory-on-chip infrared spectrometers can offer sensor advancements including raw sensing performance in addition to use such as enhanced portability. Several platforms have been proposed in the past for on-chip ethanol detection. However, selective sensing with high sensitivity at room temperature has remained a challenge. Here, we experimentally demonstrate an on-chip ethyl alcohol sensor based on a holey photonic crystal waveguide on silicon on insulator-based photonics sensing platform offering an enhanced photoabsorption thus improving sensitivity. This is achieved by designing and engineering an optical slow-light mode with a high group-index of n g  = 73 and a strong localization of modal power in analyte, enabled by the photonic crystal waveguide structure. This approach includes a codesign paradigm that uniquely features an increased effective path length traversed by the guided wave through the to-be-sensed gas analyte. This PIC-based lab-on-chip sensor is exemplary, spectrally designed to operate at the center wavelength of 3.4 μm to match the peak absorbance for ethanol. However, the slow-light enhancement concept is universal offering to cover a wide design-window and spectral ranges towards sensing a plurality of gas species. Using the holey photonic crystal waveguide, we demonstrate the capability of achieving parts per billion levels of gas detection precision. High sensitivity combined with tailorable spectral range along with a compact form-factor enables a new class of portable photonic sensor platforms when combined with integrated with quantum cascade laser and detectors.

scholarly journals High sensitivity distributed temperature fiber sensor using stimulated Brillouin scattering

2017 ◽  
Vol 25 (26) ◽  
pp. 32591 ◽  
Author(s):  
Victor Lambin Iezzi ◽  
Sebastien Loranger ◽  
Raman Kashyap
Keyword(s):  
Brillouin Scattering ◽  
Stimulated Brillouin Scattering ◽  
High Sensitivity ◽  
Fiber Sensor ◽  
Stimulated Brillouin

scholarly journals Fast Measurement of Brillouin Frequency Shift in Optical Fiber Based on a Novel Feedforward Neural Network

Photonics ◽  
2021 ◽  
Vol 8 (11) ◽  
pp. 474
Author(s):  
Fen Xiao ◽  
Mingxing Lv ◽  
Xinwan Li
Keyword(s):  
Neural Network ◽  
Optical Fiber ◽  
Frequency Shift ◽  
Brillouin Scattering ◽  
Principal Component ◽  
Feedforward Neural Network ◽  
Gain Spectrum ◽  
Fiber Sensors ◽  
Brillouin Gain ◽  
Distributed Optical Fiber

Brillouin scattering-based distributed optical fiber sensors have been successfully employed in various applications in recent decades, because of benefits such as small size, light weight, electromagnetic immunity, and continuous monitoring of temperature and strain. However, the data processing requirements for the Brillouin Gain Spectrum (BGS) restrict further improvement of monitoring performance and limit the application of real-time measurements. Studies using Feedforward Neural Network (FNN) to measure Brillouin Frequency Shift (BFS) have been performed in recent years to validate the possibility of improving measurement performance. In this work, a novel FNN that is 3 times faster than previous FNNs is proposed to improve BFS measurement performance. More specifically, after the original Brillouin Gain Spectrum (BGS) is preprocessed by Principal Component Analysis (PCA), the data are fed into the Feedforward Neural Network (FNN) to predict BFS.

Sign in / Sign up

Export Citation Format

Share Document