Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC)

Novel sources for polarisation squeezing and polarisation entanglement using photonic crystal fibres

Josip Milanovic, Mikael Lassen, Michael Förtsch, Christoph Marquardt, Ulrik L. Andersen, Gerd Leuchs

Published Jun 1, 2009• 1 citation

Abstract

Photonic crystal fibres (PCF) can be tailored to introduce a high effective nonlinear Kerr effect and to create lower amounts of excess noise compared to standard fibres. By exploiting both polarisation axes of the polarisation maintaining PCF we can generate two independent polarisation squeezed beams that can be used to create polarisation entanglement. We generated a maximum squeezing of-3.9 Aring plusmn 0.3 dB and a corresponding anti-squeezing of 16.8 Aring plusmn 0.3 dB. Furthermore we investigate the generation of polarisation squeezing in photonic crystal fibres by using a single pass setup where both the slow and fast axis has to be utilized. Taking advantage of these features and using ultrashort pulses we create polarisation squeezed states with notably higher purity than obtained in standard fibres.

DOI: 10.1109/cleoe-eqec.2009.5191598

Related papers

A novel method for polarization squeezing with Photonic Crystal Fibers

Josip Milanovic, Mikael Lassen, Ulrik L. Andersen +1 more

Photonic Crystal Fibers can be tailored to increase the effective Kerr nonlinearity, while producing smaller amounts of excess noise compared to standard silicon fibers. Using these features of Photonic Crystal Fibers we create polarization squeezed states with increased purity compared to standard fiber squeezing experiments. Explicit we produce squeezed states in counter propagating pulses along the same fiber axis to achieve near identical dispersion properties. This enables the production of polarization squeezing through interference in a polarization type Sagnac interferometer. We observe Stokes parameter squeezing of -3.9 +/-0.3dB and anti-squeezing of 16.2 +/-0.3dB.

arXiv:0902.4597Optics ExpressJan 12, 201012 citations

Polarization squeezing with photonic crystal fibers

J. Milanovic, J. Heersink, Christoph Marquardt +3 more

We report on the generation of polarization squeezing by employing intense, ultrashort light pulses in a single pass method in photonic crystal fibers. We investigated the squeezing behavior near the zero-dispersion wavelength and in the anomalous dispersion regime by using two distinct fibers. We observed a maximal squeezing at 810 nm of −3.3 ± 0.3 dB with an excess noise of +16.8 ± 0.3 dB in the anomalous regime. Correcting for linear and interference losses between the polarization modes, this corresponds to −6 ± 1 dB. The ratio of squeezing to excess noise indicates the creation of a much purer state; this ratio indeed lies an order of magnitude below those squeezing experiments that exploit traditional fibers [1]. We attribute this increased state of purity to increased effective nonlinearity and to the reduction of scattering on acoustic modes in the fiber.

Laser PhysicsApr 1, 200715 citations

An efficient source of continuous variable polarisation entanglement

Ruifang Dong, J. Heersink, Jun–ichi Yoshikawa +3 more

We have experimentally demonstrated the efficient creation of highly entangled bipartite continuous variable polarisation states. Exploiting an optimised scheme for the production of squeezing using the Kerr non-linearity of a glass fibre we generated polarisation squeezed pulses with a mean classical excitation in S3. Polarisation entanglement was generated by interfering two independent polarisation squeezed fields on a symmetric beam splitter. The resultant beams exhibit strong quantum noise correlations in the dark S1 - S2 polarisation plane. To verify entanglement generation, we characterised the quantum correlations of the system for two different sets of conjugate Stokes parameters. The quantum correlations along the squeezed and the anti-squeezed Stokes parameters were observed to be -4.1 +/- 0.3 dB and -2.6 +/- 0.3 dB below the shot noise level respectively. The degree of correlations was found to depend critically on the beam splitting ratio of the entangling beam splitter. Carrying out measurements on a different set of conjugate Stokes parameters, correlations of -3.6 +/- 0.3 dB and -3.4 +/- 0.3 dB have been observed. This result is more robust against asymmetries in the entangling beam splitter, even in the presence of excess noise.

arXiv:0709.2237Sep 14, 20071 citation

Optical Squeezing of Light in Photonic Crystal Fibres

M. Tacey

This thesis presents a comprehensive numerical investigation of polarisation squeezing in photonic crystal fibre. Squeezing is the reduction of quantum noise in one variable beyond the Heisenberg limit at the expense of increased noise in the conjugate. The greater confinement of light that is possible in photonic crystal fibres leads to a greater effective nonlinearity, which promises to yield greater quantum squeezing than is possible in standard optical fibre. There are two dominant noise sources that limit the degree of polarisation squeezing. Raman noise is the interaction of photons with phonons in the fibre medium the degree of which is characteristic of the fibre medium and scales inversely with pulse width. And guided acoustic wave Brillouin scattering is due to thermally excited mechanical eigenmodes which scales with fibre length. The larger nonlinearity of photonic crystal fibres allows shorter fibre lengths with larger pulse widths providing a means to significantly reduce the dominant noise sources and obtain polarisation squeezing beyond that of ordinary silica fibre. This thesis presents an extensive quantum treatment using the truncated Wigner method that includes loss, a non-instantaneous Raman response, excess phase-noise, second- and third- order dispersion and self-steepening to identify the physical factors that limit current photonic crystal fibre squeezing experiments and demonstrate the optimal parameters to obtain the best squeezing.

Jan 1, 20130 citations

An efficient source of continuous variable polarization entanglement

Ruifang Dong, J. Heersink, Jun–ichi Yoshikawa +3 more

We have experimentally demonstrated the efficient creation of highly entangled bipartite continuous variable polarization states. Exploiting an optimized scheme for the production of squeezing using the Kerr non-linearity of a glass fibre we generated polarization squeezed pulses with a mean classical excitation in . Polarization entanglement was generated by interfering two independent polarization squeezed fields on a symmetric beam splitter. The resultant beams exhibit strong quantum noise correlations in the dark polarization plane. To verify entanglement generation, we characterized the quantum correlations of the system for two different sets of conjugate Stokes parameters. The quantum correlations along the squeezed and the anti-squeezed Stokes parameters were observed to be −4.1±0.3 and −2.6±0.3 dB below the shot noise level, respectively. The degree of correlations was found to depend critically on the beam-splitting ratio of the entangling beam splitter. Carrying out measurements on a different set of conjugate Stokes parameters, correlations of −3.6±0.3 and −3.4±0.3 dB have been observed. This result is more robust against asymmetries in the entangling beam splitter, even in the presence of excess noise.

New Journal of PhysicsNov 14, 200733 citations

Nonlinearity in photonic crystal fibres

Chunle Xiong

This thesis introduces the linear and nonlinear properties of photonic crystal fibre (PCF), describes the fabrication and characterisation of different PCFs, and demonstrates their applications to supercontinuum (SC) generation and single-photon sources. The linear properties of PCF include endlessly single-mode transmission, highly controllable dispersion and birefringence. These unique properties have made PCFs the best media to demonstrate all kinds of nonlinear effects such as self-phase modulation (SPM), cross-phase modulation (XPM), Raman effects, four-wave mixing and modulation instability (FWM and MI), and soliton effects. The combination of these nonlinear effects has led to impressive spectral broadening known as SC generation in PCFs. The intrinsic correlation of signal and idler photons from FWM has brought PCF to the application of single-photon generation. Four projects about SC generation were demonstrated. The first was visible continuum generation in a monolithic PCF device, which gave a compact, bright (-20 dBm/nm), flat and single-mode visible continuum source extending to short wavelength at 400 nm. The second was polarised SC generation in a highly bire-fringent PCF. A well linearly polarised continuum source spanning 450-1750 nm was achieved with >99% power kept in a single linear polarisation. This polarised continuum source was then applied to tuneable visible/UV generation in a BIBO crystal. The third was residual pump peak removal for SC generation in PCFs. The fourth was to design an all-fibre dual-wavelength pumping for spectrally localised continuum generation. Two projects about photon pair generation using FWM were then demonstrated. One was an all-fibre photon pair source designed in the telecom band for quantum communication. This source achieved >50% heralding efficiency which is the highest in fibre photon pair sources reported so far. Another one was to design birefringent PCFs for naturally narrow band photon pair generation in the Si SPAD high detection efficiency range. 0.122 nm bandwidth signal photons at 596.8 nm were generated through cross polarisation phase matched FWM in a weakly birefringent PCF pumped by a picosecond Ti:Sapphire laser at 705 nm in the normal dispersion regime.

Jan 1, 20082 citations