H. Herrmann

A polarization entangled photon-pair source based on a type-II PPLN waveguide emitting at a telecom wavelength

We report the realization of a fiber-coupled polarization entangled photon-pair source at 1310 nm based on a birefringent titanium in-diffused waveguide integrated into periodically poled lithium niobate. By making use of a dedicated and high-performance setup, we characterized the quantum properties of the pairs by measuring two-photon interference in both Hong–Ou–Mandel and standard Bell inequality configurations. For the two sets of measurements we obtained interference net visibilities reaching nearly 100%, which represent important and competitive results compared to those for the similar waveguide-based configurations already reported. These results prove the relevance of our approach as an enabling technology for long-distance quantum communication.

Integrated optical source of polarization entangled photons at 1310 nm

We report the realization of a new polarization entangled photon-pair source based on a titanium-indiffused waveguide integrated on periodically poled lithium niobate pumped by a CW laser at 655 nm. The paired photons are emitted at the telecom wavelength of 1310 nm within a bandwidth of 0.7 nm. The quantum properties of the pairs are measured using a two-photon coalescence experiment showing a visibility of 85%. The evaluated source brightness, on the order of 10(5) pairs s(-1)GHz(-1)mW(-1), associated with its compactness and reliability, demonstrates the sources high potential for long-distance quantum communication.

Phase closure retrieval in an infrared-to-visible upconversion interferometer for high resolution astronomical imaging

This paper demonstrates the use of a nonlinear upconversion process to observe an infrared source through a telescope array detecting the interferometric signal in the visible domain. We experimentally demonstrate the possibility to retrieve information on the phase of the object spectrum of an infrared source by using a three-arm upconversion interferometer. We focus our study on the acquisition of phase information of the complex visibility by means of the phase closure technique. In our experimental demonstration, a laboratory binary star with an adjustable photometric ratio is used as a test source. A real time comparison between a standard three-arm interferometer and our new concept using upconversion by sum-frequency generation demonstrates the preservation of phase information which is essential for image reconstruction.

Waveguide Cavity Resonator as a Source of Optical Squeezing

We present the generation of continuous-wave optical squeezing from a titanium-indiffused lithium niobate waveguide resonator. We directly measure 2.9\pm 0.1 dB of single-mode squeezing, which equates to a produced level of 4.9\pm 0.1 dB after accounting for detection losses. This device showcases the current capabilities of this waveguide architecture and precipitates more complicated integrated continuous-wave quantum devices in the continuous-variable regime.

Modified two-photon interference achieved by the manipulation of entanglement

In this theoretical study we demonstrate that entangled states are able to significantly extend the functionality of Hong-Ou-Mandel (HOM) interferometers. By generating a coherent superposition of parametric-down-conversion photons and spatial entanglement in the input channel, the coincidence probability measured at the output changes from a typical HOM-type dip (photon bunching) into much richer patterns including an anti-bunching peak and rapid oscillation fringes with twice the optical frequency. The considered system should be realizable on a single chip using current waveguide technology in the

Nonlinear optical down- and up-conversion in PPLN waveguides for mid-infrared spectroscopy

LiNbO_3

Acousto-optically tunable integrated Ti:Er:LiNbO/sub 3/ laser

platform.

Integrated, TE- and TM-Pass, Acoustically Tunable, Double-Stage Wavelength Filters with Combined Optical/Acoustical Waveguides

Middle-infrared (MIR) spectroscopy in the 2 to 4 µm spectral range is a powerful tool in particular for environmental analysis and monitoring. However, this method suffers from missing compact, tuneable, coherent light sources and sensitive detectors. To overcome these problems to a certain extent we demonstrate consecutive nonlinear wavelength down- and up-conversion in Ti-indiffused periodically poled lithium niobate (Ti:PPLN) waveguides to generate and to detect MIR radiation [1]. In detail, nonlinear difference frequency generation (DFG) using pump and signal sources in the near infrared (NIR) is used in the transmitter. On the receiver side, we apply sum-frequency generation (SFG) to reconvert the MIR signal to the NIR.

Lithium niobate photonic wires

Wavelength tunable, narrow linewidth lasers are of growing importance for optical communication systems using wavelength-division multiplexing (WDM). A diode-pumped packaged acousto-optically tunable integrated Ti:Er:LiNbO/sub 3/ waveguide laser could be tuned (not continuously) over 31 nm in the wavelength range 1530 nm </spl lambda/<1610 nm with an emission linewidth of 0.3 nm. Here we report an improved version of the laser with a modified design; its tuning range is extended to 47 nm with a linewidth smaller than 12 pm in appropriate operating conditions adjusted.

High-power waveguide resonator second harmonic device with external conversion efficiency up to 75%

Integrated optical, acoustically tunable wavelength filters are attractive due to their narrowband filter characteristics, large tuning range, low drive power and simultaneous filtering capability. Such wavelength filters can be realized by combining acousto-optical mode converters with polarizers. In the mode converter a surface acoustic wave (SAW) with an appropriately chosen frequency yields a polarization conversion of a guided optical wave of specific wavelength to allow passing the subsequent polarizer. To improve the efficiency of the mode converter, acoustical strip waveguides can be used. We have demonstrated such an integrated optical filter with a tuning range of more than 100 nm and a filter bandwidth of less than 3 nm [1].