arXiv subjects

Connor Goham

Publications and source records attributed to Connor Goham.

3 recordsLinked to original sources

arXiv2025

Errors in PDH offset locking due to spurious spectral features

The Pound-Drever-Hall (PDH) technique is widely used to stabilize the frequency of lasers. Here we report on a routinely underestimated source of error in PDH offset-locking: a shift in the lock point due to the unintended interaction between residual optical sidebands and higher-order spatial modes in misaligned Fabry-Perot cavities. Significant frequency deviations-up to 50% of the cavity linewidth-can arise when the optical offset is obtained from a sinusoidally driven EOM. We measure this deviation experimentally, find agreement with a simple model, and show how a spectrally-pure frequency offset can reduce the deviation by an order of magnitude. Our findings draw attention to a systematic effect of importance to precision optical spectroscopy, optical clocks, and quantum information science.

physics.optics↗

arXiv2024

Spectrally-pure optical serrodyne modulation for continuously-tunable laser offset locking

The comb-like spectrum added to laser light by an electro-optic modulator (EOM) finds use in a wide range of applications, including coherent optical communication, atomic spectroscopy, and laser frequency and phase stabilization. In some cases a sideband-free optical frequency shift is preferred, such as in laser offset locking using an optical cavity, single-photon frequency shifting, and laser range finding. Approaches to obtaining an optical frequency offset (OFO) involve trade-offs between shift range, conversion gain, and suppression of spurious sidebands. Here we demonstrate an OFO of continuous-wave 871 nm laser light by serrodyne modulation using a fiber EOM and radio-frequency (RF) tones from a commercial RF system on a chip (RFSoC) to achieve shifts of 40 to 800 MHz with > 15 dB suppression of spurious sidebands and < 1.5 dB conversion loss. We also observe a smoothly varying conversion gain. The utility of this tool is demonstrated by continuously shifting the offset of a cavity-locked laser from 50 to 1600 MHz, a capability useful in spectroscopy of unknown optical transitions.

quant-ph↗

arXiv2017

Free space quantum communication with a portable quantum memory

The realization of an elementary quantum network that is intrinsically secure and operates over long distances requires the interconnection of several quantum modules performing different tasks. In this work we report the interconnection of four different quantum modules: (i) a random polarization qubit generator, (ii) a free-space quantum communication channel, (iii) an ultra-low noise portable quantum memory and (iv) a qubit decoder, in a functional elementary quantum network possessing all capabilities needed for quantum information distribution protocols. We create weak coherent pulses at the single photon level encoding polarization states $|H\rangle, |V\rangle, |D\rangle, |A\rangle$ in a randomized sequence. The random qubits are sent over a free-space link and coupled into a dual rail room temperature quantum memory and after storage and retrieval are analyzed in a four detector polarization analysis akin to the requirements of the BB84 protocol. We also show ultra-low noise and fully-portable operation, paving the way towards memory assisted all-environment free space quantum cryptographic networks.

quant-ph↗