4,794 research outputs found

    Multiple RF carrier distribution in a hybrid radio/fiber system employing a self-pulsating laser diode transmitter

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    A self-pulsating laser diode is used to generate a multicarrier microwave optical signal for use in a hybrid radio/fiber system. The self-pulsation frequency of the laser is controlled by external light injection, and can be varied between 14-24 GHz. The hybrid radio/fiber system, employing the self-pulsation laser, is used to distribute two 155-Mb/s data signals on two radio frequency (RF) carriers (at 18.5 and 18.9 GHz). Experimental results show the overall system performance for both RF channels, and demonstrate that the performance is improved by around 17 dB compared with the case when the laser is used without external injection, and thus, does not self-pulsat

    Generation of optical microwave signals using laser diodes with enhanced modulation response for hybrid radio/fiber systems

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    The authors present the idea of using a laser with improved modulation bandwidth to generate microwave optical signals for hybrid radio/fibre systems. External light injection has been used to enhance the frequency response of the laser and thus greatly improve the overall performance of the hybrid system. Experimental results show an 8 dB improvement in system performance for the externally injected laser in a hybrid radio/fibre system used for distributing 155 Mbit/s data signals on an 18 GHz carrie

    Optomechanical transduction of an integrated silicon cantilever probe using a microdisk resonator

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    Sensitive transduction of the motion of a microscale cantilever is central to many applications in mass, force, magnetic resonance, and displacement sensing. Reducing cantilever size to nanoscale dimensions can improve the bandwidth and sensitivity of techniques like atomic force microscopy, but current optical transduction methods suffer when the cantilever is small compared to the achievable spot size. Here, we demonstrate sensitive optical transduction in a monolithic cavity-optomechanical system in which a sub-picogram silicon cantilever with a sharp probe tip is separated from a microdisk optical resonator by a nanoscale gap. High quality factor (Q ~ 10^5) microdisk optical modes transduce the cantilever's MHz frequency thermally-driven vibrations with a displacement sensitivity of ~ 4.4x10^-16 m\sqrt[2]{Hz} and bandwidth > 1 GHz, and a dynamic range > 10^6 is estimated for a 1 s measurement. Optically-induced stiffening due to the strong optomechanical interaction is observed, and engineering of probe dynamics through cantilever design and electrostatic actuation is illustrated

    Improved performance of a hybrid radio/fiber system using a directly modulated laser transmitter with external injection

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    A directly modulated laser diode with external light injection is used to generate microwave optical signals for a hybrid radio/fiber system. The external light injection greatly enhances the frequency response of the laser, and thus, significantly improves the overall performance of the hybrid system. Experimental results show a 14-dB improvement in system performance for the externally injected laser in a hybrid radio/fiber communication link used for distributing 155-Mb/s data signal

    Acousto-optic and opto-acoustic modulation in piezo-optomechanical circuits

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    Acoustic wave devices provide a promising chip-scale platform for efficiently coupling radio frequency (RF) and optical fields. Here, we use an integrated piezo-optomechanical circuit platform that exploits both the piezoelectric and photoelastic coupling mechanisms to link 2.4 GHz RF waves to 194 THz (1550 nm) optical waves, through coupling to propagating and localized 2.4 GHz acoustic waves. We demonstrate acousto-optic modulation, resonant in both the optical and mechanical domains, in which waveforms encoded on the RF carrier are mapped to the optical field. We also show opto-acoustic modulation, in which the application of optical pulses gates the transmission of propagating acoustic waves. The time-domain characteristics of this system under both pulsed RF and pulsed optical excitation are considered in the context of the different physical pathways involved in driving the acoustic waves, and modeled through the coupled mode equations of cavity optomechanics.Comment: 8 pages, 6 figure

    Photo-detectors integrated with resonant tunneling diodes

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    We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 μm in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD’s NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.info:eu-repo/semantics/publishedVersio

    Photo-detectors integrated with resonant tunneling diodes

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    We report on photo-detectors consisting of an optical waveguide that incorporates a resonant tunneling diode (RTD). Operating at wavelengths around 1.55 m in the optical communications C band we achieve maximum sensitivities of around 0.29 A/W which is dependent on the bias voltage. This is due to the nature of RTD nonlinear current-voltage characteristic that has a negative differential resistance (NDR) region. The resonant tunneling diode photo-detector (RTD-PD) can be operated in either non-oscillating or oscillating regimes depending on the bias voltage quiescent point. The oscillating regime is apparent when the RTD-PD is biased in the NDR region giving rise to electrical gain and microwave self-sustained oscillations Taking advantage of the RTD's NDR distinctive characteristics, we demonstrate efficient detection of gigahertz (GHz) modulated optical carriers and optical control of a RTD GHz oscillator. RTD-PD based devices can have applications in generation and optical control of GHz low-phase noise oscillators, clock recovery systems, and fiber optic enabled radio frequency communication systems.FCT under the project WOWi [PTDC/EEA-TEL/100755/2008]; programme POCTI/FEDER [REEQ/1272/EEI/2005]; FCT Portugal [SFRH/BPD/84466/2012]info:eu-repo/semantics/publishedVersio

    Optical signal processing via two-photon absorption in a semiconductor microcavity for the next generation of high-speed optical communications network

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    Due to the introduction of new broadband services, individual line data rates are expected to exceed 100 Gb/s in the near future. To operate at these high speeds, new optical signal processing techniques will have to be developed. This paper will demonstrate that two-photon absorption in a specially designed semiconductor microcavity is an ideal candidate for optical signal processing applications such as autocorrelation, sampling, and demultiplexing in high-speed wavelength-division-multiplexed (WDM) and hybrid WDM/optical time-division-multiplexed networks
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