arXiv subjects

Malcolm B. Gray

Publications and source records attributed to Malcolm B. Gray.

6 recordsLinked to original sources

arXiv2005

Quantum Noise Locking

Quantum optical states which have no coherent amplitude, such as squeezed vacuum states, can not rely on standard readout techniques to generate error signals for control of the quadrature phase. Here we investigate the use of asymmetry in the quadrature variances to obtain a phase-sensitive readout and to lock the phase of a squeezed vacuum state, a technique which we call noise locking (NL). We carry out a theoretical derivation of the NL error signal and the associated stability of the squeezed and anti-squeezed lock points. Experimental data for the NL technique both in the presence and absence of coherent fields are shown, including a comparison with coherent locking techniques. Finally, we use NL to enable a stable readout of the squeezed vacuum state on a homodyne detector.

quant-ph↗

arXiv2005

Demonstration of a passive sub-picostrain fiber strain sensor

We demonstrate a fiber Fabry-Perot (FFP) sensor capable of detecting sub-picostrain signals, from 100 Hz and extending beyond 100 kHz, using the Pound-Drever-Hall frequency locking technique. A low power diode laser at 1550 nm is locked to a free-space reference cavity to suppress its free-running frequency noise, thereby stabilizing the laser. The stabilized laser is then used to interrogate a FFP where the PDH error signal yields the instantaneous fiber strain.

physics.optics↗

arXiv2004

Pump-probe differencing technique for cavity-enhanced, noise-canceling saturation laser spectroscopy

We present an experimental technique enabling mechanical-noise free, cavity-enhanced frequency measurements of an atomic transition and its hyperfine structure. We employ the 532nm frequency doubled output from a Nd:YAG laser and an iodine vapour cell. The cell is placed in a traveling-wave Fabry-Perot interferometer (FPI) with counter-propagating pump and probe beams. The FPI is locked using the Pound-Drever-Hall (PDH) technique. Mechanical noise is rejected by differencing pump and probe signals. In addition, this differenced error signal gives a sensitive measure of differential non-linearity within the FPI.

physics.optics↗

arXiv2004

Interrogation of a fiber Fabry-Perot sensor by current modulation of a diode laser

We present a method for remote interrogation of passive fiber Bragg grating Fabry-Perot resonators, employing current modulation of the diode laser source. With the presence of both RF amplitude and frequency modulation, it is a variant of the ultra-sensitive Pound-Drever-Hall laser frequency locking technique. We demonstrate that current modulation and interferometric demodulation removes the need for a phase modulator in the sensing architecture.

physics.optics↗

arXiv2004

Phase-sensitive interrogation of fiber Bragg grating resonators for sensing applications

We discuss a phase-sensitive technique for remote interrogation of passive Bragg grating Fabry-Perot resonators. It is based on Pound-Drever-Hall laser frequency locking, using radio-frequency phase modulation sidebands to derive an error signal from the complex optical response, near resonance, of a Fabry-Perot interferometer. We examine how modulation frequency and resonance bandwidth affect this error signal. Experimental results are presented that demonstrate when the laser is locked, this method detects differential phase shifts in the optical carrier relative to its sidebands, due to minute fiber optical path displacements.

physics.optics↗

arXiv1998

Suppression of Classical and Quantum Radiation Pressure Noise via Electro-Optic Feedback

We present theoretical results that demonstrate a new technique to be used to improve the sensitivity of thermal noise measurements: intra-cavity intensity stabilisation. It is demonstrated that electro-optic feedback can be used to reduce intra-cavity intensity fluctuations, and the consequent radiation pressure fluctuations, by a factor of two below the quantum noise limit. We show that this is achievable in the presence of large classical intensity fluctuations on the incident laser beam. The benefits of this scheme are a consequence of the sub-Poissonian intensity statistics of the field inside a feedback loop, and the quantum non-demolition nature of radiation pressure noise as a readout system for the intra-cavity intensity fluctuations.

quant-ph↗