Active temporal and spatial multiplexing of photons
G. J. Mendoza et al.
Abstract
The maturation of many photonic technologies from individual components to next-generation system-level circuits will require exceptional active control of complex states of light. A prime example is in quantum photonic technology: while single-photon processes are often probabilistic, it has been shown in theory that rapid and adaptive feedforward operations are sufficient to enable scalability. Here, we use simple “off-the-shelf” optical components to demonstrate active multiplexing—adaptive rerouting to single modes—of eight single-photon “bins” from a heralded source. Unlike other possible implementations, which can be costly in terms of resources or temporal delays, our new configuration exploits the benefits of both time and space degrees of freedom, enabling a significant increase in the single-photon emission probability. This approach is likely to be employed in future near-deterministic photon multiplexers with expected improvements in integrated quantum photonic technology.
Narrowband cw injection seeded high power femtosecond double-pass optical parametric generator at 43 MHz: Gain and noise dynamics
H. Linnenbank, T. Steinle, and H. Giessen
Abstract
We demonstrate narrowband cw injection seeding of a femtosecond double-pass optical parametric generator at 43 MHz repetition rate with a simple, low power external cavity diode laser. Up to 2.5 W of near-IR radiation (1.5 – 1.66 µm) as well as 800 mW of tunable mid-IR radiation (2.75 – 3.15 µm) with pulse durations below 300 fs are generated with a remarkable pulse-to-pulse and long term power stability. Compared to conventional, vacuum noise seeded optical parametric generators, the presented frequency conversion scheme does not only exhibit superior gain and noise dynamics, but also a high degree of flexibility upon control parameters such as pump power, seed power, or spectral position of the seed.
Experimental demonstration of high-dimensional photonic spatial entanglement between multi-core optical fibers
H. Lee, S. Choi, and H. Park
Abstract
Fiber transport of multi-dimensional photonic qudits promises high information capacity per photon without space restriction. This work experimentally demonstrates transmission of spatial qudits through multi-core optical fibers and measurement of the entanglement between two fibers with quantum state analyzers, each composed of a spatial light modulator and a single-mode fiber. Quantum state tomography reconstructs the four-dimension entangled state that verifies the non-locality through concurrences in two-dimensional subspaces and a high-dimensional Bell-type CGLMP inequality.
In-field entanglement distribution over a 96 km-long submarine optical fibre
S. Wengerowsky, S. K. Joshi, F. Steinlechner, J. R. Zichi, S. M. Dobrovolskiy, R. v. d. Molen, J. W. N. Los, V. Zwiller, M. A. M. Versteegh, A. Mura, D. Calonico, M. Inguscio, H. Hübel, A. Zeilinger, A. Xuereb, R. Ursin
Abstract
Techniques for the distribution of quantum-secured cryptographic keys have reached a level of maturity allowing them to be implemented in all kinds of environments, away from any form of laboratory infrastructure. Here, we detail the distribution of entanglement between Malta and Sicily over a 96 km-long submarine telecommunications optical fibre cable. We used this standard telecommunications fibre as a quantum channel to distribute polarisation-entangled photons and were able to observe around 257 photon pairs per second, with a polarisation visibility above 90%. Our experiment demonstrates the feasibility of using deployed submarine telecommunications optical fibres as long-distance quantum channels for polarisation-entangled photons. This opens up a plethora of possibilities for future experiments and technological applications using existing infrastructure.
Improvement to Sellmeier equation for periodically poled LiNbO3 crystal using mid-infrared difference-frequency generation
L.H. Deng, X.M. Gao, Z.S. Cao, W.D. Chen, Y.Q. Yuan, W.J. Zhang and Z.B. Gong
Abstract
Improvement to the Sellmeier equation for the extraordinary index of periodically poled LiNbO3 crystal (PPLN) is reported. The equation has been improved based on a continuous tunable mid-infrared radiation realizing in a PPLN crystal using difference-frequency-generation (DFG) and quasi-phase-matching (QPM) technique. The improved equation is suitable to estimate the QPM conditions of PPLN crystal for temperatures between 25 °C and 180 °C and mid-infrared wavelengths ranging from 2.8 μm to 4.8 μm.
A difference frequency generation spectrometer and its detection of atmospheric N2O
Z. Cao, X. Gao, L. Deng, W.D. Chen, Y. Yuan, W. Zhang and Z. Gong
Abstract
The paper reports the realization and characterization of a difference frequency generation spectrometer using periodically poled lithium niobate (PPLN) crystal. The pump and signal laser we used is a Ti:sapphire ring laser and a diode pumped monolithic Nd:YAG laser, respectively. The continuous wave (cw) infrared radiation from 2.8 to 4.8 μm has been generated. The idler radiation can be used to study fundamental absorption bands of molecules and trace gas detection. In this work, we report the detection of nitrous oxide (N2O) in atmosphere, the minimum detectable concentration of 10.9 ppbV was achieved using a Herriott cell with the optical path length of 100 m.
Mid-infrared laser absorption spectrometers based upon all-diode laser difference frequency generation and a room temperature quantum cascade laser for the detection of CO, N2O and NO
V.L. Kasyutich, R.J. Holdsworth and P.A. Martin
Abstract
We describe the performance of two mid-infrared laser spectrometers for carbon monoxide, nitrous oxide and nitric oxide detection. The first spectrometer for CO and N2O detection around 2203 cm-1 is based upon all-diode laser difference frequency generation (DFG) in a quasi-phase matched periodically-poled lithium niobate (PPLN) crystal using two continuous-wave room-temperature distributed feedback diode lasers at 859 and 1059 nm. We also report on the performance of a mid-infrared spectrometer for NO detection at 1900 cm-1 based upon a thermoelectrically-cooled continuous-wave distributed feedback quantum cascade laser (QCL). Both spectrometers had a single-pass optical cell and a thermoelectrically cooled HgCdZnTe photovoltaic detector. Typical minimum detection limits of 2.8 ppmv for CO, 0.6 ppmv for N2O and 2.7 ppmv for NO have been demonstrated for a 100 averaged spectra acquired within 1.25 s and a cell base length of 21 cm at 100 Torr. Noise-equivalent absorptions of 10-5 and 10-4 Hz-1/2 are typically demonstrated for the QCL and the DFG based spectrometers, respectively.
Study of quasi-phase matching wavelength acceptance bandwidth for periodically poled LiNbO3 crystal-based difference-frequency generation
Z. Cao, X. Gao, W. Chen, H. Wang, W. Zhang and Z. Gong
Abstract
The temperature tuning characteristics of quasi-phase matching (QPM) wavelength acceptance bandwidth in a uniform periodically poled lithium niobate (PPLN) based on difference-frequency generation (DFG) are studied theoretically and experimentally. This paper proposes a PPLN device consisting of several segments of different temperatures to obtain a more desirable performance for the QPM-DFG. The result shows that through the tuning of temperature, the bandwidth can be changed considerably and the method was proved suitable and accurate to calculate QPM wavelength acceptance bandwidth of DFG in a uniform PPLN crystal for temperatures between room temperature and 180 °C and mid-infrared (mid-IR) wavelengths ranging from 2.8 to 4.8 µm.
Pump-enhanced difference-frequency generation at 3.3 μm
M. F. Witinski, J. B. Paul, and J. G. Anderson
Abstract
The demonstration of continuous wave intracavity difference-frequency generation in the mid-infrared (mid-IR) is presented. A cavity for pump laser enhancement is constructed around a periodically poled lithium niobate crystal, and the cavity length is locked to the frequency of the pump laser using the Pound-Drever-Hall technique, producing a gain of 12 in the resultant idler power compared to the single-pass case. A widely tunable single-mode 3.3 μm idler beam with a power of nearly 10 mW is available for direct absorption spectroscopy. The pump-enhancement method demonstrated here should be readily scalable to produce hundreds of milliwatts of mid-IR light by using higher power signal and pump lasers.
A DFG-based cavity ring-down spectrometer for trace gas sensing in the mid-infrared
K. E. Whittaker, L. Ciaffoni, G. Hancock, R. Peverall and G. A. D. Ritchie
Abstract
Continuing studies into an all-diode laser-based 3.3µm difference frequency generation cavity ring-down spectroscopy system are presented. Light from a 1,560 nm diode laser, amplified by an erbium-doped fibre amplifier, was mixed with 1,064 nm diode laser radiation in a bulk periodically poled lithium niobate crystal to generate 16µW of mid-IR light at 3,346 nm with a conversion efficiency of 0.05%W-1cm-1. This radiation was coupled into a 77 cm long linear cavity with average mirror reflectivities of 0.9996, and a measured baseline ring-down time of 6.07±0.03µs. The potential of such a spectrometer was illustrated by investigating the P(3) transition in the fundamental 3F2 band of CH4 both in a 7.5 ppmv calibrated mixture of CH4 in air and in breath samples from methane and non-methane producers under conditions where the minimum detectable absorption coefficient (αmin) was 2.8 x 10-8cm-1 over 6 s using a ring-down time acquisition rate of 20 Hz. Allan variance measurements indicated an optimum αmin of 2.9 x 10-9cm-1 over 44 s.
