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[IEEE 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz2018) - Nagoya, Japan (2018.9.9-2018.9.14)] 2018 43rd International Conference on Infrared, Millimeter, and Terahertz Waves (IRMMW-THz) - Tuneable Optical Frequency Comb Generator for THz Spectroscopy
摘要： We present an optical frequency comb generator with a record span of 3.8 THz suitable for high resolution THz spectroscopy, based on a single phase modulator system. The line spacing, exactly referenced to a microwave synthesizer, can be continuously tuned from 17.5 GHz to 20 GHz overcoming the limitation otherwise imposed by the free spectral range of the fibre loop, making the system capable of generating a continuously tuneable electrical signal from 122.5 GHz to >2.7 THz. The system noise has been measured up to a record frequency of 300 GHz, and shown to be limited by the multiplied phase noise of the reference synthesizer.
关键词： THz spectroscopy,tuneable,heterodyne signal,phase modulator,optical frequency comb generator
更新于2025-09-23 15:21:01
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Ultra-Wide and Flattened Optical Frequency Comb Generation Based on Cascaded Phase Modulator and LiNbO3-MZM Offering Terahertz Bandwidth
摘要： In this paper, a new technique for generation of ultra-wide and flattened optical frequency comb (OFC) based on serial cascading of a phase modulator and dual-driven Lithium-Niobate Mach Zehnder modulator (DD-LiNbO3-MZM) is proposed. Over 60 carriers were generated by carefully adjusting the RF switching voltage (RFSV) of the DD-LiNbO3-MZM and the signal frequency of the sinusoidal wave (RF) source. A low power amplified RF source with a signal driving power of ~16.9dBm is applied, and the power of CW laser is kept at 3dBm. The frequency spacing (FS) is kept at 20GHz for generating the maximum number of carriers. Nonetheless, the scheme is also tested for the FSs of 64GHz, and 32GHz. Each scenario is examined in simulation environment and the main outcomes are highlighted. The proposed scheme is comparatively simple and the FS varies with the applied RF source on the modulators. The achieved OFC lines have a tone-to-noise ratio (TNR) of over ~45dB with an undesired side mode suppression ratio of approximately 20dB. The comb lines are almost flat with a varying power deviation of around 0dB-6dB which is optimized to nearly ~0.12dB. Furthermore, the impact of the RFSV on the generated number of carriers is studied in detail. The scheme is analyzed in terms of cost efficiency, power deviations, TNR, optical signal to noise ratio, and number of achieved comb lines.
关键词： Optical Frequency Comb,Mach-Zehnder modulator,Phase modulator,Intensity modulation
更新于2025-09-23 15:19:57
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[IEEE 2019 International Topical Meeting on Microwave Photonics (MWP) - Ottawa, ON, Canada (2019.10.7-2019.10.10)] 2019 International Topical Meeting on Microwave Photonics (MWP) - Phase Noise Performance of SILPLL based Opto-electronic Oscillator using Sagnac-loop PM-IM Convertor
摘要： Forced opto-electronic oscillators (OEO) are important component in future telecommunications and instrumentation systems. Most OEO are realized using intensity modulators (IM) with recent interest shifting to phase modulators (PM). A comprehensive analysis of Sagnac loop based OEO is presented, where phase is converted to intensity (PM-IM). This paper evaluates phase noise performance of SILPLL OEO in terms of Sagnac loop component errors and its impact on the PM-IM conversion. Results are presented for a 10 GHz SILPLL based OEO.
关键词： Phase modulator,Sagnac Loop,PM-IM conversion,Opto-electronic oscillators
更新于2025-09-12 10:27:22
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Dynamic metasurface based cavity structures for enhanced absorption and phase modulation
摘要： Metasurface based optical cavity structures consist of a metallic metasurface realized on top of a dielectric slab backed with a metal plane. Such structures have been employed in the design of optical devices such as flat lenses, wave plates and holograms at frequencies from microwave to mid-infrared. Recently, such structures with dynamically reconfigurable optical characteristics have been explored for electrically tunable optical absorption and reflection phase modulation. To date, absorption modulation and phase modulation have been realized with large insertion loss. In this work, we employ an analytical approach based on transmission line theory where the metasurface is represented by a surface admittance. We extend the above approach for the design and analysis of under and over coupled resonance regimes in metasurface cavity structure. This enables a mutual design of cavity thickness and individual metasurface for large amplitude or phase modulation. A dynamic metasurface based optical cavity is experimentally demonstrated at THz frequencies where the dynamic metasurface consists of metallic resonators embedded with thin film vanadium dioxide patches. By driving insulator to metal transition in vanadium dioxide, the THz optical response of the metasurface based cavity structure is modulated. The fabricated device exhibits perfect absorption modulation and reflection phase modulation up to 180°. The reported results demonstrate the potential of such structures for realizing novel devices such as tunable holograms, high-efficiency modulators and frequency tunable filters at THz. The analytical approach presented here can be applied for analysis and design of metasurface cavity structures based on other material systems at frequencies ranging from THz to mid-infrared.
关键词： Terahertz,Phase modulator,Dynamic metasurface,Perfect absorption modulator,Metasurface optical cavity
更新于2025-09-10 09:29:36