scholarly journals Dispersion engineering and measurement of whispering gallery mode microresonator for Kerr frequency comb generation

Nanophotonics ◽  
2020 ◽  
Vol 9 (5) ◽  
pp. 1087-1104 ◽  
Author(s):  
Shun Fujii ◽  
Takasumi Tanabe
Keyword(s):  
Continuous Wave ◽  
Frequency Tuning ◽  
Frequency Comb ◽  
Whispering Gallery Mode ◽  
High Repetition Rate ◽  
Power Efficient ◽  
Frequency Combs ◽  
Dispersion Engineering ◽  
Whispering Gallery ◽  
Wide Range

AbstractDesigning and engineering microresonator dispersion are essential for generating microresonator frequency comb. Microresonator frequency combs (microcombs, Kerr frequency combs) offer the potential for various attractive applications as a new type of coherent light source that is power efficient and compact and has a high repetition rate and a broad bandwidth. They are easily driven with a continuous-wave pump laser with adequate frequency tuning; however, the resonators must have a high quality (Q) factor and suitable dispersion. The emergence of cavity enhanced four-wave mixing, which is based on third-order susceptibility in the host material, results in the generation of broadband and coherent optical frequency combs in the frequency domain equivalent to an optical pulse in the time domain. The platforms on which Kerr frequency combs can be observed have been developed, thanks to intensive efforts by many researchers over a few decades. Ultrahigh-Q whispering gallery mode (WGM) microresonators are one of the major platforms since they can be made of a wide range of material including silica glass, fluoride crystals and semiconductors. In this review, we focus on the dispersion engineering of WGM microresonators by designing the geometry of the resonators based on numerical simulation. In addition, we discuss experimental methods for measuring resonator dispersion. Finally, we describe experimental results for Kerr frequency combs where second- and higher-order dispersions influence their optical spectra.

scholarly journals Spectral Broadening in a Continuously Pumped Singly Resonant Second-Harmonic Cavity

2021 ◽  
Vol 11 (15) ◽  
pp. 7122
Author(s):  
Simona Mosca ◽  
Tobias Hansson ◽  
Maria Parisi
Keyword(s):  
Continuous Wave ◽  
Frequency Comb ◽  
Second Harmonic ◽  
Input Power ◽  
Second Order ◽  
Optical Frequency ◽  
Frequency Combs ◽  
Research Areas ◽  
Mixed Regime ◽  
Wide Range

Optical frequency comb synthesizers with a wide spectral range are an essential tool for many research areas such as spectroscopy, precision metrology, optical communication, and sensing. Recent studies have demonstrated the direct generation of frequency combs, via second-order processes, that are centered on two different spectral regions separated by an octave. Here, we present the capability of optical quadratic frequency combs for broad-bandwidth spectral emission in unexplored regimes. We consider comb formation under phase-matched conditions in a continuous-wave pumped singly resonant second-harmonic cavity, with large intracavity power and control of the detuning over several cavity line widths. The spectral analysis reveals quite distinctive sidebands that arise far away from the pump, singularly or in a mixed regime together with narrowband frequency combs. Notably, by increasing the input power, the optical frequency lines evolve into widely spaced frequency clusters, and at maximum power, they appear in a wavelength range spanning up to 100 nm. The obtained results demonstrate the power of second-order nonlinearities for direct comb production within a wide range of pump wavelengths.

scholarly journals Power-efficient generation of two-octave mid-IR frequency combs in a germanium microresonator

Nanophotonics ◽  
2018 ◽  
Vol 7 (8) ◽  
pp. 1461-1467 ◽  
Author(s):  
Yuhao Guo ◽  
Jing Wang ◽  
Zhaohong Han ◽  
Kazumi Wada ◽  
Lionel C. Kimerling ◽  
...  
Keyword(s):  
Pump Power ◽  
Frequency Comb ◽  
Wide Band ◽  
Power Efficient ◽  
Frequency Combs ◽  
Dispersion Engineering ◽  
High Pump Power ◽  
High Pump ◽  
Limited Power ◽  
Comb Generation

AbstractOctave-spanning frequency comb generation in the deep mid-infrared (>5.5 μm) typically requires a high pump power, which is challenging because of the limited power of narrow linewidth lasers at long wavelengths. We propose twofold dispersion engineering for a Ge-on-Si microcavity to enable both dispersion flattening and dispersion hybridization over a wide band from 3.5 to 10 μm. A two-octave mode-locked Kerr frequency comb can be generated from 2.3 to 10.2 μm, with a pump power as low as 180 mW. It has been shown that dispersion flattening greatly enhances the spectral broadening of the generated comb, whereas dispersion hybridization improves its spectral flatness.

scholarly journals Optical whispering-gallery mode barcodes for high-precision and wide-range temperature measurements

2021 ◽  
Vol 10 (1) ◽  
Author(s):  
Jie Liao ◽  
Lan Yang
Keyword(s):  
High Precision ◽  
Dynamic Range ◽  
Single Mode ◽  
Whispering Gallery Mode ◽  
Temperature Measurements ◽  
Laser Source ◽  
Multiple Modes ◽  
Whispering Gallery ◽  
Wide Range ◽  
Thermal Sensing

AbstractTemperature is one of the most fundamental physical properties to characterize various physical, chemical, and biological processes. Even a slight change in temperature could have an impact on the status or dynamics of a system. Thus, there is a great need for high-precision and large-dynamic-range temperature measurements. Conventional temperature sensors encounter difficulties in high-precision thermal sensing on the submicron scale. Recently, optical whispering-gallery mode (WGM) sensors have shown promise for many sensing applications, such as thermal sensing, magnetic detection, and biosensing. However, despite their superior sensitivity, the conventional sensing method for WGM resonators relies on tracking the changes in a single mode, which limits the dynamic range constrained by the laser source that has to be fine-tuned in a timely manner to follow the selected mode during the measurement. Moreover, we cannot derive the actual temperature from the spectrum directly but rather derive a relative temperature change. Here, we demonstrate an optical WGM barcode technique involving simultaneous monitoring of the patterns of multiple modes that can provide a direct temperature readout from the spectrum. The measurement relies on the patterns of multiple modes in the WGM spectrum instead of the changes of a particular mode. It can provide us with more information than the single-mode spectrum, such as the precise measurement of actual temperatures. Leveraging the high sensitivity of WGMs and eliminating the need to monitor particular modes, this work lays the foundation for developing a high-performance temperature sensor with not only superior sensitivity but also a broad dynamic range.

scholarly journals Repetition frequency locking of a terahertz quantum cascade laser emitting at 4.2 THz

2020 ◽  
Vol 13 (1) ◽  
pp. 32-40
Author(s):  
Wen Guan ◽  
Ziping Li ◽  
Kang Zhou ◽  
Wenjian Wan ◽  
Xiaoyu Liao ◽  
...  
Keyword(s):  
Quantum Cascade Laser ◽  
Continuous Wave ◽  
Frequency Comb ◽  
Signal To Noise Ratio ◽  
Phase Lock Loop ◽  
Wave Mode ◽  
Repetition Frequency ◽  
Frequency Locking ◽  
Frequency Combs ◽  
Quantum Cascade

The electrically-pumped terahertz quantum cascade laser (QCL) is characterized by high power emission, compact, broad frequency coverage, and so on, which shows abilities for frequency comb operations. Although free-running QCLs can work as frequency combs by designing the laser structure with small group velocity dispersions and/or inserting mirrors to compensate laser intrinsic dispersions, the ideal comb operation can only be obtained by firmly locking the repetition frequency and carrier frequency of a laser. In this work, we have reported a repetition frequency locking of a terahertz QCL emitting around 4.2 THz. When the 6-mm-long laser is operated in continuous wave mode without any locking techniques, the repetition frequency is measured to be ~6.15 GHz with a linewidth of hundred kilohertz. Once a phase lock loop (PLL) is applied to dynamically control the drive current of the QCL, we have demonstrated a successful repetition frequency locking of the laser with a signal to noise ratio of 80 dB. This technique can be employed for the frequency comb and dual-comb operations of terahertz QCLs for high-resolution applications.

scholarly journals Dynamics of microresonator frequency comb generation: models and stability

Nanophotonics ◽  
2016 ◽  
Vol 5 (2) ◽  
pp. 231-243 ◽  
Author(s):  
Tobias Hansson ◽  
Stefan Wabnitz
Keyword(s):  
Continuous Wave ◽  
Temporal Dynamics ◽  
Frequency Comb ◽  
Modulational Instability ◽  
Theoretical Models ◽  
Light Sources ◽  
Generation Process ◽  
Modal Expansion ◽  
Frequency Combs ◽  
Comb Generation

AbstractMicroresonator frequency combs hold promise for enabling a new class of light sources that are simultaneously both broadband and coherent, and that could allow for a profusion of potential applications. In this article, we review various theoretical models for describing the temporal dynamics and formation of optical frequency combs. These models form the basis for performing numerical simulations that can be used in order to better understand the comb generation process, for example helping to identify the universal combcharacteristics and their different associated physical phenomena. Moreover, models allow for the study, design and optimization of comb properties prior to the fabrication of actual devices. We consider and derive theoretical formalisms based on the Ikeda map, the modal expansion approach, and the Lugiato-Lefever equation. We further discuss the generation of frequency combs in silicon resonators featuring multiphoton absorption and free-carrier effects. Additionally, we review comb stability properties and consider the role of modulational instability as well as of parametric instabilities due to the boundary conditions of the cavity. These instability mechanisms are the basis for comprehending the process of frequency comb formation, for identifying the different dynamical regimes and the associated dependence on the comb parameters. Finally, we also discuss the phenomena of continuous wave bi- and multistability and its relation to the observation of mode-locked cavity solitons.

Fabrication, Characterization and Microsensing of Whispering-Gallery Mode Micro-Coupling Systems

2008 ◽  
Author(s):  
Qiulin Ma ◽  
Tobias Rossmann ◽  
Zhixiong Guo
Keyword(s):  
Transmission Loss ◽  
Coupling Efficiency ◽  
High Sensitivity ◽  
Single Mode ◽  
Whispering Gallery Mode ◽  
Single Mode Fiber ◽  
Whispering Gallery ◽  
Coupling System ◽  
Wide Range ◽  
Micro Sensor

An optical micro-coupling system of whispering-gallery mode usually consists of a resonator (e.g. a sphere) and a coupler (e.g. a taper). In this report, silica microspheres of 50–500 μm in diameter are fabricated by hydrogen flame fusing of an end of a single mode fiber or fiber taper. Fiber tapers are fabricated by the method of heating and pulling that meets an adiabatic condition. Taper’s waist diameter can routinely be made less than 1 μm and almost zero transmission loss in a taper is achieved which allows an effective and phase-matched coupling for a wide range sizes of microspheres. Both resonators and couplers’ surface microstructure and shapes are examined by scanning electronic microscopy. Three regimes of coupling are achieved, enabling a good flexibility to control Q value and coupling efficiency of a micro-coupling system. Whispering gallery mode shift is used to demonstrate a novel temperature micro-sensor. Its sensitivity determined from actual experimental results agrees well with the theoretical value. A concept of using the photon’s cavity ring down (CRD) in the microsphere to make a novel high-sensitivity trace gas micro-sensor is proposed. The CRD time constant when ammonia is chosen as the analyte gas is predicted using the simulated absorption lines.

Dispersion tailoring of a crystalline whispering gallery mode microcavity for a wide-spanning optical Kerr frequency comb

2016 ◽  
Vol 33 (9) ◽  
pp. 1913 ◽  
Author(s):  
Yosuke Nakagawa ◽  
Yuta Mizumoto ◽  
Takumi Kato ◽  
Tomoya Kobatake ◽  
Hiroki Itobe ◽  
...  
Keyword(s):  
Frequency Comb ◽  
Whispering Gallery Mode ◽  
Whispering Gallery

scholarly journals A taxonomy of optical dissipative structures in whispering-gallery mode resonators with Kerr nonlinearity

2018 ◽  
Vol 376 (2124) ◽  
pp. 20170381 ◽  
Author(s):  
Irina V. Balakireva ◽  
Yanne K. Chembo
Keyword(s):  
Laser Field ◽  
Continuous Wave ◽  
Kerr Nonlinearity ◽  
Whispering Gallery Mode ◽  
Dissipative Structures ◽  
Basins Of Attraction ◽  
Theme Issue ◽  
Whispering Gallery ◽  
Spatio Temporal

In this paper, the research related to the formation of optical dissipative structures in Kerr-nonlinear whispering-gallery mode resonators pumped with continuous-wave lasers is reviewed. Pattern formation in these systems can be analysed using the paradigmatic Lugiato–Lefever model, which is a partial differential equation ruling the dynamics of the intra-cavity laser field. Various dissipative structures such as Turing rolls, solitons, breathers and spatio-temporal chaos can emerge in the resonator depending on the laser power and frequency. The bifurcation analysis enables a classification of these patterns, and also permits identification of their basins of attraction. This article is part of the theme issue ‘Dissipative structures in matter out of equilibrium: from chemistry, photonics and biology (part 1)’.

scholarly journals Comb-locked frequency-swept synthesizer for high precision broadband spectroscopy

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Riccardo Gotti ◽  
Thomas Puppe ◽  
Yuriy Mayzlin ◽  
Julian Robinson-Tait ◽  
Szymon Wójtewicz ◽  
...  
Keyword(s):  
Continuous Wave ◽  
Gas Sensing ◽  
Frequency Comb ◽  
Probe Laser ◽  
Line Center ◽  
Frequency Combs ◽  
Promising Tool ◽  
Multiple Species ◽  
Spectral Ranges ◽  
Broadband Spectroscopy

Abstract Frequency combs have made optical metrology accessible to hundreds of laboratories worldwide and they have set new benchmarks in multi-species trace gas sensing for environmental, industrial and medical applications. However, current comb spectrometers privilege either frequency precision and sensitivity through interposition of a cw probe laser with limited tuning range, or spectral coverage and measurement time using the comb itself as an ultra-broadband probe. We overcome this restriction by introducing a comb-locked frequency-swept optical synthesizer that allows a continuous-wave laser to be swept in seconds over spectral ranges of several terahertz while remaining phase locked to an underlying frequency comb. This offers a unique degree of versatility, as the synthesizer can be either repeatedly scanned over a single absorption line to achieve ultimate precision and sensitivity, or swept in seconds over an entire rovibrational band to capture multiple species. The spectrometer enables us to determine line center frequencies with an absolute uncertainty of 30 kHz and at the same time to collect absorption spectra over more than 3 THz with state-of-the-art sensitivity of a few 10−10 cm−1. Beyond precision broadband spectroscopy, the proposed synthesizer is an extremely promising tool to force a breakthrough in terahertz metrology and coherent laser ranging.

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