Injection locking

About: Injection locking is a research topic. Over the lifetime, 4567 publications have been published within this topic receiving 60942 citations.

Advanced Interferometry for Gravitational Wave Detection

Abstract: In this thesis we investigate advanced techniques for the readout and control of various interferometers. In particular, we present experimental investigations of interferometer configurations and control techniques to be used in second generation interferometric gravitational wave detectors. We also present a new technique, tilt locking, for the readout and control of optical interferometers. We report the first experimental demonstration of a Sagnac interferometer with resonant sideband extraction (RSE). We measure the frequency response to modulation of the length of the arms and demonstrate an increase in signal bandwidth of by a factor of 6.5 compared to the Sagnac with arm cavities only. We compare Sagnac interferometers based on optical cavities with cavity-based Michelson interferometers and find that the Sagnac configuration has little overall advantage in a cavity-based system. A system for the control and signal extraction of a power recycled Michelson interferometer with RSE is presented. This control system employs a frontal modulation scheme requiring a phase modulated carrier field and a phase modulated subcarrier field. The system is capable of locking all 5 length degrees of freedom and allows the signal cavity to be detuned over the entire range of possibilities, in principle, whilst maintaining lock. We analytically investigate the modulation/demodulation techniques used to obtain these error signals, presenting an introductory explanation of single sideband modulation/demodulation and double demodulation. This control system is implemented on a benchtop prototype interferometer. We discuss technical problems associated with production of the input beam modulation components and present several solutions. Operation of the interferometer is demonstrated for a wide range of detunings. The frequency response of the interferometer is measured for various detuned points and we observe good agreement with theoretical predictions. The ability of the control system to maintain lock as the interferometer is detuned is experimentally demonstrated. Tilt locking, a new technique to obtain an error signal to lock a laser to an optical cavity, is presented. This technique produces an error signal by efficient measurement of the interference between the TEM00 and TEM10 modes. We perform experimental and theoretical comparisons with the widely used Pound-Drever-Hall (PDH) technique. We derive the quantum noise limit to the sensitivity of a measurement of the beam position, and using this result calculate the shot noise limited sensitivity of tilt locking. We show that tilt locking has a quantum efficiency of 80%, compared to 82% for the PDH technique. We present experimental demonstrations of tilt locking in several applications including frequency stabilisation, continuous-wave second harmonic generation, and injection locking of a Nd:YAG slab laser. In each of these cases, we demonstrate that the performance of tilt locking is not the limiting factor of the lock stability, and show that it achieves similar performance to the PDH based system. Finally, we discuss how tilt locking can be effectively applied to two beam interferometers. We show experimentally how a two beam interferometer typically gives excellent isolation against errors arising from changes in the photodetector position, and exper-

Stability of mode locked states of coupled oscillator arrays

Abstract: A method for analyzing beat frequency entrained (or mode locked) systems of coupled nonlinear oscillators is presented. Stable mode locked states are almost periodic oscillations that occur outside of the fundamental entrainment region of the array, and generate a periodic pulse train when the oscillator outputs are summed. The analysis relates the stability of the states to the relationship between the frequency pullings and the time average phases of the oscillators. The method is applied to three mode locked Van der Pol oscillators with arbitrary coupling time delay, and shows that the mode locking bandwidth is maximized for specific values of coupling delay and oscillator nonlinearity parameter. >

Analysis of a homodyne receiver using an injection-locked semiconductor laser

Abstract: The authors study an optical homodyne receiver using an injection-locked semiconductor laser as a local oscillator. The carrier recovery process introduces a phase error, and the calculation of its statistical properties leads to the evaluation of the receiver performance. The analysis shows the dependence of the receiver performance on the injected power and the phase detuning, between the transmitter, and local oscillator electric fields. The receiver performance is affected by the phase noises of the transmitter and local oscillators, by the shot noise of the detectors in the receiver, and by the modulation noise resulting from the injection locking of the local oscillator by a modulated signal. >

On the Synchronization Condition for Superharmonic Coupled QVCOs

Abstract: A steady-state nonlinear analysis of quadrature voltage-controlled oscillators (QVCOs) comprising two VCOs mutually coupled at their second-harmonic frequency through a direct coupling circuit is presented. The analysis is based on an accurate prediction of the behavior of each VCO, which is analyzed separately as an injection locked oscillator taking into account both higher order harmonics of the differential tank voltage and the effect of the common-mode voltage at the drain terminals. We show that synchronization of the two VCOs is possible only at a frequency, derived in closed-form, which differs appreciably from the tank's resonant frequency.

Remote beating of parallel or orthogonally polarized dual-wavelength optical carriers for 5G millimeter-wave radio-over-fiber link.

Abstract: A novel millimeter-wave radio over fiber (MMW-RoF) link at carrier frequency of 35-GHz is proposed with the use of remotely beating MMW generation from reference master and injected slave colorless laser diode (LD) carriers at orthogonally polarized dual-wavelength injection-locking. The slave colorless LD supports lasing one of the dual-wavelength master modes with orthogonal polarizations, which facilitates the single-mode direct modulation of the quadrature amplitude modulation (QAM) orthogonal frequency division multiplexing (OFDM) data. Such an injected single-carrier encoding and coupled dual-carrier transmission with orthogonal polarization effectively suppresses the cross-heterodyne mode-beating intensity noise, the nonlinear modulation (NLM) and four-wave mixing (FWM) sidemodes during injection locking and fiber transmission. In 25-km single-mode fiber (SMF) based wireline system, the dual-carrier under single-mode encoding provides baseband 24-Gbit/s 64-QAM OFDM transmission with an error vector magnitude (EVM) of 8.8%, a bit error rate (BER) of 3.7 × 10-3, a power penalty of <1.5 dB. After remotely self-beating for wireless transmission, the beat MMW carrier at 35 GHz can deliver the passband 16-QAM OFDM at 4 Gbit/s to show corresponding EVM and BER of 15.5% and 1.4 × 10-3, respectively, after 25-km SMF and 1.6-m free-space transmission.