Titanium-diffused Lithium Niobate Waveguide Research Articles

Fabrication limits of waveguides in nonlinear crystals and their impact on quantum optics applications

Waveguides in nonlinear materials are a key component for photon pair sources and offer promising solutions to interface quantum memories through frequency conversion. To bring these technologies closer to every-day life, it is still necessary to guarantee a reliable and efficient fabrication of these devices. Therefore, a thorough understanding of the technological limitations of nonlinear waveguiding devices is paramount. In this paper, we study the link between fabrication errors of waveguides in nonlinear crystals and the final performance of such devices. In particular, we first derive a mathematical expression to qualitatively assess the technological limitations of any nonlinear waveguide. We apply this tool to study the impact of fabrication imperfections on the phasematching properties of different quantum processes realized in titanium-diffused lithium niobate waveguides. Finally, we analyse the effect of waveguide imperfections on quantum state generation and manipulation for few selected cases. Studying the impact of fabrication errors on the waveguide widths, we find that the presence of correlated noise plays a major role in the degradation of the phasematching and we suggest different possible strategies to reduce the impact of fabrication imperfections.

Programmable Coupler Ladder Based on Lithium Niobate Y-Junction Reflector

This paper presents a proposal for a novel integrated tunable coupler device called programmable coupler ladder, based on Titanium diffused lithium niobate waveguide and Y-junction reflector. Unlike the traditional serial to parallel converter, the coupler ladder sorts the output bits in the time axis using a built-in delay waveguide. With a proper control signal it can perform signal processing at the bit level. It also can generate coherent multi-channel outputs with theoretically arbitrary amplitude and phase from continuous input light source. Its application in optical microwave beam forming is briefly described. The key component, built-in delay line based on Y-junction reflector, has been experimentally verified via a loop resonator structure. I dB loss is found for each Y-junction reflector, which enables a practical coupler ladder. The loop itself is also an important device for optical signal processing.

All-optical switching based on cascading of second-order nonlinearities in a periodically poled titanium-diffused lithium niobate waveguide

We report efficient all-optical switching by using a periodically poled titanium-diffused lithium niobate (Ti:PPLN) waveguide. The periodically domain inversion of the Ti:PPLN waveguide is achieved by electric field poling. The switching is driven by the second-order nonlinear effect of the cascading of phase-matched sum-frequency-generation and difference-frequency-generation processes. It is found that about 12% of the signal is switched by a 20-W gate power.

Ultrathin (5 µm) Flexible Reflective Waveplate of Fluorinated Polyimide and Elimination of Polarization Sensitivity in Titanium-Diffused Lithium Niobate Waveguide Circuits

An ultrathin, flexible reflective half-waveplate, consisting of a 5-µm-thick polyimide quarter-waveplate sputtered with a thin gold film, was fabricated, and its property of eliminating polarization sensitivity in titanium-diffused lithium niobate waveguide circuits was investigated. Transverse electric/transverse magnetic mode-conversion ratios of 15–20 dB at 1.55 µm were obtained, and a polarization-insensitive intensity modulator with a low half-wave voltage of 4.5 V was successfully fabricated using a titanium-diffused lithium niobate waveguide. The excess loss of the polyimide reflective waveplate (1 dB) was much smaller than that using a conventional quartz waveplate (6 dB).

Waveguide electrooptic switch arrays

A review is presented of electrooptic waveguide switch arrays with strong emphasis on those based on titanium-diffused lithium niobate waveguides. Crosspoint and array design considerations and performance are discussed as are waveguide technology limits. Switch array demonstrations are reviewed. Experimental demonstrations of switch arrays are described and particular parameters of the array, including insertion loss, crosstalk, and switching voltage achieved by several laboratories, are discussed and compared. Results of high-speed switch arrays are also described.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Proton-exchanged Fresnel lenses in Ti:LiNbO_3 waveguides

Fresnel lenses were fabricated by the patterned proton-exchange technique in titanium-diffused lithium niobate waveguides. The large change in refractive index available with the proton exchange allows fabrication of a high-efficiency thin Fresnel lens. Lens characteristics of nearly diffraction-limited focus spot size and efficiency up to 70% were obtained. The use of the lens to construct an integrated-optic rf spectrum analyzer of 1-GHz bandwidth and 2-MHz resolution is also demonstrated.

Efficient single-mode fiber to titanium diffused lithium niobate waveguide coupling for λ = 1.32 µm

We report detailed results on the achievement of very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers. By determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss, we have achieved total measured fiber-waveguide-fiber insertion loss as low as 1 dB for a 1 cm long waveguide at <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">\lambda = 1.32 \mu</tex> m. The relative contributions of coupling and propagation loss are determined. Very good correlation is found between the coupling loss and the match between the fiber and waveguide mode dimensions. Design data for diffusion parameters to obtain good mode match for arbitrary fiber dimension are presented.

Efficient Single-Mode Fiber to Titanium Diffused Lithium Niobate Waveguide Coupling for Lambda = l.32 µm

We report detailed results on the achievement of very high optical throughput for titanium diffused lithium niobate waveguides coupled between input and output single-mode fibers. By determining appropriate diffusion parameters to obtain excellent dimensional match between the fiber and waveguide modes and simultaneously low propagation loss, we have achieved total measured fiber-waveguide-fiber insertion loss as low as 1 dB for a 1 cm long waveguide at Lambda = 1.32 µm. The relative contributions of coupling and propagation loss are determined. Very good correlation is found between the coupling loss and the match between the fiber and waveguide mode dimensions. Design data for diffusion parameters to obtain good mode match for arbitrary fiber dimension are presented.

High efficiency single-mode fibre to Ti:LiNbO3 waveguide coupling

We have achieved a single-mode fibre to waveguide to fibre total insertion loss as low as 1 dB for a 1 cm-long titanium-diffused lithium niobate waveguide.