Si photonic wire waveguides are attractive for constructing various optical devices that are extremely small because the waveguides can be bent with extremely small curvatures of less than a few micrometers of bending radius. We have fabricated optical directional couplers with the waveguides and demonstrated their fundamental characteristics. Their coupling length was extremely short, several micrometers, because of strong optical coupling between the waveguide cores. We have also demonstrated wavelength-demultiplexing functions for these devices with a long coupled waveguide. Optical outputs from a device with a 100-mum-long coupled waveguide changed reciprocally with a 20-nm wavelength spacing between the parallel and cross ports. We also demonstrated the operation of ultrasmall optical add-drop multiplexers (OADMs) with Bragg grating reflectors made up of the waveguides. The dropping wavelength bandwidth of the OADMs was less than 0.7 nm, and these dropping wavelengths could be precisely designed by adjusting the grating period. Using the Si photonic wire waveguide, we have also demonstrated thermo-optic switches. Metal thin-film heaters were evaporated onto the branch of a Mach-Zehnder interferometer that incorporated the waveguide to achieve switching operations by thermo-optic effects. In these switching operations, we observed more than 30 dB of extinction ratio, less than 90 mW of switching power, and less than 100 mus of switching speed

/pdf/si-photonic-wire-waveguide-devices-43q9umzaom.pdf

Si Photonic Wire Waveguide Devices

We fabricated optical directional couplers with Si-wire waveguides and demonstrated their fundamental characteristics. Their coupling-length was extremely short, several micrometers, because of strong optical coupling between the waveguide cores. Wavelength demultiplexing functions were also demonstrated for devices with a long coupled waveguide. Optical output from a device 800 /spl mu/m long changed reciprocally with 2.5-nm wavelength spacing between the parallel and cross ports.

http://tera.yonsei.ac.kr/class/2012_2_2/test_result.files/20120919_directional_couplers_Jeong-Min_Lee.pdf

Optical directional coupler based on Si-wire waveguides

Glasses, either pure or suitably doped, constitute an excellent material for the development of integrated optical circuits. A brief review is presented of the most widely used processes for the fabrication of passive and active glass waveguides. Brilliant prospects of glass-based platforms for the development of photonic integrated circuits are outlined.

https://www.spiedigitallibrary.org/journals/optical-engineering/volume-53/issue-7/071819/Glass-optical-waveguides-a-review-of-fabrication-techniques/10.1117/1.OE.53.7.071819.pdf

Glass optical waveguides: a review of fabrication techniques

Embodiments of the present invention provide a highly uniform low cost production worthy solution for manufacturing low propagation loss optical waveguides on a substrate. In one embodiment, the present invention provides a method of forming a PSG optical waveguide on an undercladding layer of a substrate that includes forming at least one silicate glass optical core on said undercladding layer using a plasma enhanced chemical vapor deposition process including a silicon source gas, an oxygen source gas, and a phosphorus source gas, wherein the oxygen source gas and silicon source gas have a ratio of oxygen atoms to silicon atoms greater than 20:1.

Method of forming a phosphorus doped optical core using a PECVD process

Devices and methods for the vapor deposition of amorphous, silicon-containing thin films (31) using vapors comprised of deuterated species. Thin films grown on a substrate wafer (32) by this method contain deuterium but little to no hydrogen. Optical devices comprised of optical waveguides (31) formed using this method have significantly reduced optical absorption or loss in the near-infrared optical spectrum commonly used for optical communications, compared to the loss in waveguides formed in thin films grown using conventional vapor deposition techniques with hydrogen containing precursors. In one variation, the optical devices (31) are formed on a silicon-oxide layer (33) that is formed on a substrate (32), such as a silicon substrate. The optical devices of some variations are of the chemical species SiOxNy:D. Since the method of formation requires no annealing, the thin films can be grown on electronic and optical devices or portions thereof without damaging those devices.

Use of deuterated gases for the vapor deposition of thin films for low-loss optical devices and waveguides

A method for fabricating an optical waveguide, comprising the following steps. That is, forming an optical waveguide on surface of a substrate via an atmospheric pressure chemical vapor deposition (AP-CVD) method using a silica raw material containing an organic material, and irradiating ultraviolet light on at least a portion of that optical waveguide. The refractive index of the portion of the optical waveguide irradiated with ultraviolet light increases. Since changing the refractive index in this way enables the formation of a diffraction grating, it is possible to manufacture optical filters and wavelength dispersion devices.

Optical waveguide fabrication method

An optical add-drop multiplexer with a gratingloaded directional coupler in silica waveguides is demonstrated. The device for this configuration has a large fabrication tolerance and is small in size. A new scheme, in which the coupling length of the directional coupler is twice the complete coupling length, enables low cross-talk for both add and drop operations. This device is polarization-independent due to its relatively lowtemperature process. key words: Bragg grating, silica waveguide, optical add-drop

An Optical Add-Drop Multiplexer with a Grating-Loaded Directional Coupler in silica Waveguides

By using a Mach-Zehnder interferometer, we evaluated photosensitivity in silica-based waveguides deposited by atmospheric pressure vapor deposition. Our results show that photosensitivity with ArF excimer laser irradiation was ten times greater than photosensitivity with KrF excimer laser irradiation. ArF excimer laser irradiation induced a refractive-index change of greater than 2 x 10(-3) at 1.55 mum and a birefringence between TE and TM modes of less than 6 x 10(-5). It has also been determined that the photoinduced absorption change of 90 dB/mm at 210 nm cannot account for a refractive-index change greater than 10(-3).

Photosensitivity in silica-based waveguides deposited by atmospheric pressure chemical vapor deposition.

PROBLEM TO BE SOLVED: To lessen the influence of the reflected light of UV rays at the time of forming a diffraction grating, etc., by utilizing photoirradiation refractive index modulation, by forming an absorption layer to UV light between a plane substrate and an optical waveguide. SOLUTION: A Ge-added quartz glass layer 14 is formed between the optical waveguide consisting of a core 11, an upper clad 12 and a lower clad 13 and an Si substrate 10. The upper and lower clad layers 12 and 13 have the refractive index lower than the refractive index of the core 11. The core 11 is irradiated with UV light 16 through a phase mask 17, to generate the refractive index modulation in the core 11. Usually, the UV light 16 past the optical waveguide is reflected by the substrate surface and is again cast as return light 18 to the core 11. Since the return light 18 is different from an ideal intensity distribution, the contrast of the refractive index modulation by the photoirradiation degrades. The Ge-added quartz glass layer 14 which is the absorption layer to the UV light 16 is, thereupon, disposed between the optical waveguide and the Si substrate 10, by which the return light 18 may be decreased.

Takashi Saito

Papers

Optical waveguide fabrication method

An Optical Add-Drop Multiplexer with a Grating-Loaded Directional Coupler in silica Waveguides

Photosensitivity in silica-based waveguides deposited by atmospheric pressure chemical vapor deposition.

Optical circuit and its production

Photo-Induced Refractive Index Change in Silica Based Waveguide Deposited by APCVD with ArF and KrF Excimer Laser