David W. Nippa

Generation and Modulation of a 94-GHz Signal Using Electrooptic Modulators

Wireless data transmission at 10.6 Gb/s on a 94-GHz carrier is achieved using photonic components operating at frequencies less than 18 GHz, including a laser diode, two lithium niobate modulators, and an arrayed waveguide grating. A uni- traveling-carrier photodiode is used to convert the doubly modulated optical signal to a modulated millimeter-wave (mmW) carrier. Two antennas are used to transmit and receive the data-encoded mmW signal. A Schottky-diode detector is used to detect the on-off keyed data on the mmW signal at power levels greater than -20 dBm. MMW wireless signals are measured out to a distance of 800 m.

Data Transmission Using Differential Phase-Shift Keying on a 92 GHz Carrier

Wireless data transmission with binary phase-shift keying modulation encoded on a 92 GHz carrier is achieved using photonic components. A high-speed photodiode is used to convert the doubly-modulated optical signal to a modulated millimeter-wave carrier. A W-band Mach-Zehnder interferometer with a one-bit time delay is used to directly detect the differential phase-shift keyed millimeter-wave wireless signal without the use of a local oscillator. Field tests with antennas separated by 890 m demonstrate the ability to discriminate two phase states for differential binary phase shift keying (DBPSK) and four phase states for differential quadrature phase shift keying (DQPSK) at data rates of 2.3 Gb/s and 4.6 Gb/s, respectively.

A multiplexed light-matter interface for fibre-based quantum networks

Processing and distributing quantum information using photons through fibre-optic or free-space links are essential for building future quantum networks. The scalability needed for such networks can be achieved by employing photonic quantum states that are multiplexed into time and/or frequency, and light-matter interfaces that are able to store and process such states with large time-bandwidth product and multimode capacities. Despite important progress in developing such devices, the demonstration of these capabilities using non-classical light remains challenging. Here, employing the atomic frequency comb quantum memory protocol in a cryogenically cooled erbium-doped optical fibre, we report the quantum storage of heralded single photons at a telecom-wavelength (1.53 μm) with a time-bandwidth product approaching 800. Furthermore, we demonstrate frequency-multimode storage and memory-based spectral-temporal photon manipulation. Notably, our demonstrations rely on fully integrated quantum technologies operating at telecommunication wavelengths. With improved storage efficiency, our light-matter interface may become a useful tool in future quantum networks.

Design of a 10-Gb/s satellite downlink at millimeter-wave frequencies

System requirements, including carrier frequency, transmitted power and antenna gain are presented for a 10 Gb/s satellite downlink operating at millimeter-wave frequencies. Telecommunications-grade optical components and a high-speed photodiode are used to generate and modulate millimeter-wave carrier frequencies between 90 GHz and 100 GHz at data rates in excess of 10 Gb/s. Experimental results are presented that determine the minimum received power level needed for error-free wireless data transmission. Commercially available W-band power amplifiers are shown to increase the transmitted power level and extend the error-free propagation distance to distances of 10 km. Experimental results and documented atmospheric attenuation values for clouds, fog and rain are used to estimate link budgets for a wireless downlink located on a low-earth-orbiting satellite operating at an altitude of 350 km.

Modulation of light using Kerr-clad silica waveguide

A silica waveguide employing an electrooptic Kerr material as a functioning cladding is shown to modulate light at RF frequencies. The modulator uses a Kerr electrooptic material as the functional cladding on a silica waveguide structure. The modulator is designed to operate at 70 C and the electrooptic material has an index of refraction that is less than the silica waveguide at that temperature. Kerr-based materials have a refractive index that varies as the square of the applied voltage. This quadratic relationship is exploited by combining a DC bias voltage with the RF drive signal in order to reduce the drive voltage of the modulator.

The integration of modulators and multiplexers on silica planar lightwave circuits

An integrated optical device comprising two arrayed waveguide gratings (AWGs) and an electrooptic modulator array is described. When used in conjunction with a broadband light source, the integrated optic device can provide multiple high data rate signals from a single optical light source. The first AWG spectrally slices the light from the broadband light source. Each optical signal is then modulated using an electrooptically-clad silica waveguide Mach-Zehnder interferometer. The second AWG multiplexes the modulated optical signals onto a single output fiber. The paper describes the design of the modulator-multiplexer circuit. Experimental results of the modulator portion of the circuit show the modulation of light at 1550 nm in a electrooptically-clad silica waveguide at data rates of 1 GB/s.

Development of photon pair sources using periodically poled lithium niobate waveguide technology and fiber optic components

To support quantum technologies that require entangled photon pairs and/or heralded photons for operation, a photon pair source was developed that uses periodically poled lithium niobate (PPLN) waveguides that are coupled to optical fibers. Both Ti-indiffused and annealed proton-exchanged (APE) waveguide technologies were studied, and waveguide/fiber interfaces were designed to increase the coupling efficiency of the photon pairs into optical fiber. PPLN waveguide devices were fabricated and the optical loss, wavelength conversion efficiency, and heralding efficiency were measured. The maximum heralding efficiencies achieved were 75 and 68% for Ti-indiffused and APE waveguides, respectively. A compact photon pair source based on a packaged PPLN waveguide device and commercially available fiber optic components is presented.

Enhancement of solar cell efficiency by spectral-conversion using rare earth-metal nanoclusters

A novel organic/inorganic nanocomposite is proposed as a luminescent material of a spectral converter (SC) for improving the energy conversion efficiency of solar cells. The nanocomposite consists of a polymer matrix doped with rare earth-centered heterometallic alkoxides, rare earth (RE)-metal (M) nanocluster. The excitation edge of Eu3+ was found to be extended from about 400 nm to 470 nm by adding Michlers ketone to the nanocomposite. The broadening of the excitation wavelength range enhanced the energy conversion efficiency of a single-crystalline Si solar cell by 9.9 %. Also it was found that Eu-M nanocluster can emit broad-band luminescence ranging from 400 nm to 600 nm in addition to the narrow-bands luminescence peculiar to Eu3+ when M is selected. Such controllability in both excitation and emission spectra could make it possible to use the nanocomposite doped with RE-M nanocluster as a luminescent material for SCs for various solar cells having different spectral responses.

Integrated Optical Approaches to Millimeter-Wave Generation and Modulation

Two lithium niobate modulators and an arrayed waveguide grating are used to generate a millimeter-wave carrier at 94 GHz and to encode a 10 GB/s data stream onto the carrier for wireless data transport.

Four-Waveguide Variable Optical Attenuator

A liquid-crystal electrooptic top cladding material is placed over a silica waveguide to form a 4 mm-long variable optical attenuator that provides 15 dB extinction, 4 ms response time, and less than 1 dB PDL.