Observation of injection locking in an optomechanical rf oscillator

Injection locking of a radiation-pressure optomechanical oscillator is demonstrated through external modulation of the optical pump power near the optomechanical oscillation frequency. It is shown that the frequency and phase of a microtoroidal optomechanical oscillator can be locked to those of an electronic oscillator (or any other signal) that can modulate the optical input power and whose frequency is within the lock range

Solid-state lasers for coherent communication and remote sensing

Semiconductor-diode laser-pumped solid-state lasers have properties that are superior to other lasers for the applications of coherent communication and remote sensing. These properties include efficiency, reliability, stability, and capability to be scaled to higher powers. We have demonstrated that an optical phase-locked loop can be used to lock the frequency of two diode-pumped 1.06 micron Nd:YAG lasers to levels required for coherent communication. Monolithic nonplanar ring oscillators constructed from solid pieces of the laser material provide better than 10 kHz frequency stability over 0.1 sec intervals. We have used active feedback stabilization of the cavity length of these lasers to demonstrate 0.3 Hz frequency stabilization relative to a reference cavity. We have performed experiments and analysis to show that optical parametric oscillators (OPO's) reproduce the frequency stability of the pump laser in outputs that can be tuned to arbitrary wavelengths. Another measurement performed in this program has demonstrated the sub-shot-noise character of correlations of the fluctuations in the twin output of OPO's. Measurements of nonlinear optical coefficients by phase-matched second harmonic generation are helping to resolve inconsistency in these important parameters

Systematic methodology for the global stability analysis of nonlinear circuits

A new methodology for the detection of Hopf, flip, and turning-point bifurcations in nonlinear circuits analyzed with harmonic balance (HB) is presented. It enables a systematic determination of bifurcation loci in terms of relevant parameters, such as input power, input frequency, and bias voltages, for instance. It does not rely on the use of continuation techniques and is able to globally provide the entire loci, often containing multivalued sections and/or disconnected curves, in a single simulation. The calculation of Hopf and flip bifurcations is based on the extraction of a small-signal admittance/impedance function from HB and the calculation of its zeros through a geometrical procedure. The method is ideally suited for the investigation of the global stability properties of power amplifiers and other nonlinear circuits. The turning-point locus, associated with either jump phenomena or synchronization, is obtained by taking into account the annihilation/generation of steady-state solutions that is inherent to this type of bifurcation. A technique is also presented for the exhaustive calculation of oscillation modes in multidevice oscillators and oscillators loaded with multiresonance networks. The new methodologies are illustrated through their application to a power amplifier and a multimode oscillator.This work was supported by the Spanish Ministry of Economy and Competitiveness and the European Regional Development Fund (ERDF/FEDER) under research projects TEC2014-60283-C3-1-R and TEC2017-88242-C3-1-R

Active locking and entanglement in type II optical parametric oscillators

Type II optical parametric oscillators are amongst the highest-quality sources of quantum-correlated light. In particular, when pumped above threshold, such devices generate a pair of bright orthogonally-polarized beams with strong continuous-variable entanglement. However, these sources are of limited practical use, because the entangled beams emerge with different frequencies and a diffusing phase difference. It has been proven that the use of an internal wave-plate coupling the modes with orthogonal polarization is capable of locking the frequencies of the emerging beams to half the pump frequency, as well as reducing the phase-difference diffusion, at the expense of reducing the entanglement levels. In this work we characterize theoretically an alternative locking mechanism: the injection of a laser at half the pump frequency. Apart from being less invasive, this method should allow for an easier real-time experimental control. We show that such an injection is capable of generating the desired phase locking between the emerging beams, while still allowing for large levels of entanglement. Moreover, we find an additional region of the parameter space (at relatively large injections) where a mode with well defined polarization is in a highly amplitude-squeezed state

Techniques for low jitter clock multiplication

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2008.Includes bibliographical references (p. 115-121).Phase realigning clock multipliers, such as Multiplying Delay-Locked Loops (MDLL), offer significantly reduced random jitter compared to typical Phase-Locked Loops (PLL). This is achieved by introducing the reference signal directly into their voltage controlled oscillators (VCO) to realign the phase to the clean reference. However, the typical cost of this benefit is a significant increase in deterministic jitter due to path mismatch in the detector as well as analog nonidealities in the tuning circuits. This thesis proposes a mostly-digital tuning technique that drastically reduces deterministic jitter in phase realigning clock multipliers. The proposed technique eliminates path mismatch by using a single-path digital detection method that leverages a scrambling time-to-digital converter (TDC) and correlated double sampling to infer the tuning error from the difference in cycle periods of the output. By using a digital loop filter that consists of a digital accumulator, the tuning technique avoids the analog nonidealities of typical tuning paths. The scrambling TDC is not a contribution of this thesis. A highly-digital MDLL prototype that uses the proposed tuning technique consists of two custom 0.13 [mu]m ICs, an FPGA board, a discrete digital-to-analog converter (DAC) with effective 8 bits, and a simple RC filter. The measured performance (for a 1.6 GHz output and 50 MHz reference) demonstrated an overall jitter of 0.93 ps rms, and estimated random and deterministic jitter of 0.68 ps rms and 0.76 ps peak-to-peak, respectively. The proposed MDLL architecture is especially suitable for digital ICs, since its highly-digital architecture is mostly compatible with digital design flows, which eases its porting between technologies.by Belal Moheedin Helal.Ph.D