Reflective-type photonic displacement sensor incorporating a micro-optic beam shaper.

A reflective-type photonic displacement sensor has been proposed and realized by taking advantage of a compact optical sensing head that incorporates a micro-optic beam shaper in conjunction with a rotary scale. The miniature beam shaper, which includes a pair of aspheric lenses, plays the role of optimally focusing a light beam emitted by a VCSEL source onto a rotary scale by utilizing efficient collimating optics. The focused beam is selectively reflected by a periodic grating pattern relevant to the scale; the beam then arrives at the photodetector (PD) receiver. Hence, an arbitrary displacement, encoded by the scale, could readily translate into an output signal available from the receiver. The proposed sensor was thoroughly designed through ray tracing based simulations and then analyzed in terms of the alignment tolerance for the VCSEL and code scale. The slim beam shaper was cost effectively constructed using plastic injection molding, and it was precisely integrated with the VCSEL and PD in a passive alignment manner, in order to complete the optical sensing head. In order to construct the displacement sensor, a code-wheel type scale containing alternate patterns of high- and low-reflection, was integrated with the optical head. The sensor was primarily characterized with respect to the evolution of generated beams for single-mode (SM) and multi-mode (MM) VCSELs, taking into consideration that the modulation depth of the output signal is elevated with decreasing focused beam size. For an embodied displacement sensor based on an SM VCSEL, leading to a focused beam spot of ~30 µm, a well-defined output with a modulation depth of 7% was obtained in response to the displacement of the rotary scale engraved with a grating of 10-µm pitch. The linear and angular resolutions were accordingly estimated to be better than 5 µm and 0.02°, respectively.

Highly efficient active optical interconnect incorporating a partially chlorinated ribbon POF in conjunction with a visible VCSEL.

A low-loss 4-ch active optical interconnect (AOI) enabling passive alignment was proposed and built resorting to a transmitter (Tx) incorporating a red 680-nm VCSEL, which is linked to a receiver (Rx) module via a partially chlorinated ribbon POF. The POF was observed to exhibit an extremely low loss of ~0.24 dB/m at λ = 680 nm, in comparison to ~1.29 dB/m at λ = 850 nm, and a large numerical aperture of ~0.42. Both the Tx and Rx, which taps into a beam router based on collimated beam optics involving a pair of spherical lenses, were meant to be substantially alignment tolerant and compact. The achieved tolerance for the constructed modules was beyond 40 µm in terms of the positioning of VCSEL and photodetector. The proposed AOI was completed by linking the Tx with the Rx via a 3-m long ribbon POF, incurring a transmission loss of as small as 3.2 dB. The AOI was practically assessed in terms of a high-speed data transmission over a wide range of temperatures and then exploited to convey full HD video signals.

Si3N4 waveguide-based parallel optical interconnect incorporating an interface comprising arrayed grating couplers combined with fiber arrays.

A high-speed parallel optical interconnect (POI) incorporating silicon nitride (Si(3)N(4)) waveguides was realized that takes advantage of an eight-channel input/output interface based on grating couplers (GCs) in alignment with fiber arrays. For each of the channels, a straight waveguide in the middle is linked to a GC via a taper, which is addressed by a single-mode fiber (SMF) at the input and a multimode fiber at the output. To verify the feasibility of the interconnect, the alignment tolerance has been explored in terms of the position and angle of incidence of the SMF with respect to the GC. This has been conducted by probing into the optical throughput of the proposed POI, which is determined by different sources of loss associated with the proposed Si(3)N(4) waveguide device. For a typical GC, the measured coupling loss was 5.2 dB at the center wavelength of 1590 nm, when addressed by a SMF. For a 1 dB loss penalty, the positional tolerance of the fiber was discovered to about ±3 µm and 45 µm along the lateral direction and the direction inclined at 16 deg normal to the device, respectively. The corresponding angular tolerance was ±1 deg. We ultimately confirmed that 8×10 Gbps high-speed digital signals were efficiently delivered through the proposed POI.

CWDM based HDMI interconnect incorporating passively aligned POF linked optical subassembly modules.

A four-channel transmitter OSA (TOSA) and a receiver optical sub-assembly (ROSA) module were presented. They take advantage of a coarse WDM (CWDM) scheme, employing two types of VCSELs at 780 and 850 nm, where no wavelength filters are involved in the TOSA. The ROSA and TOSA were constructed through a fully passive alignment process using components produced by virtue of a cost effective plastic injection molding technique. In order to build a high quality optical HDMI interconnect, four channel optical links between these modules ware established via two graded-index plastic optical fibers (GI-POFs). The HDMI interconnect was thoroughly evaluated in terms of the alignment tolerance, the light beam propagation, and the data transmission capability. For the ROSA, the measured tolerance, as affected by the photodiode alignment, was ~45 µm and over 200 µm for the transverse and longitudinal directions, respectively. For the TOSA, the tolerance, which is mostly dependent upon the VCSEL alignment, was ~20 µm and more than 200 µm for the transverse and longitudinal directions, respectively. The beam profiles for the TOSA and ROSA were monitored to confirm their feasibility from the optical coupling perspective. A digital signal at 2.5 Gb/s was efficiently transmitted through the HDMI interconnect with a bit error ratio of below 10-16. A 1080p HDMI signal from a Blu-ray player was delivered through the interconnect to an LCD monitor and successfully displayed a high quality video.

Ribbon plastic optical fiber linked optical transmitter and receiver modules featuring a high alignment tolerance.

Ribbon plastic optical fiber (POF) linked four-channel optical transmitter (Tx) and receiver (Rx) modules have been proposed and realized featuring an excellent alignment tolerance. The two modules share a common configuration involving an optical sub-assembly (OSA) with vertical cavity surface emitting lasers (VCSELs)/photodetectors (PDs), and their driver ICs, which are integrated onto a single printed circuit board (PCB) substrate. The OSA includes an alignment structure, a beam router and a fiber guide, which were produced by using plastic injection molding. We have accomplished a fully passive alignment between the VCSELs/PDs and the ribbon POF by taking advantage of the alignment structure that serves as a reference during the alignment of the constituent parts of the OSA. The electrical link, which largely determines the operation speed, has been remarkably shortened, due to a direct wire-bonding between the VCSELs/PDs and the driver circuits. The light sources and the detectors can be individually positioned, thereby overcoming the pitch limitations of the ribbon POF, which is made up of perfluorinated graded-index (GI) POF with a 62.5 µm core diameter. The overall alignment tolerance was first assessed by observing the optical coupling efficiency in terms of VCSEL/PD misalignment. The horizontal and vertical 3-dB alignment tolerances were about 20 µm and 150 µm for the Tx and 50 µm and over 200 µm for the Rx, respectively. The VCSEL-to-POF coupling loss for the Tx and the POF-to-PD loss for the Rx were 3.25 dB and 1.35 dB at a wavelength of 850 nm, respectively. Subsequently, a high-speed signal at 3.2 Gb/s was satisfactorily delivered via the Tx and Rx modules over a temperature range of -30 to 70°C with no significant errors; the channel crosstalk was below -30 dB. Finally, the performance of the prepared modules was verified by transmitting a 1080p HDMI video supplied by a Bluelay player to an LCD TV.

Silicon photonic temperature sensor employing a ring resonator manufactured using a standard CMOS process.

An ultra-small integrated photonic temperature sensor has been proposed and demonstrated which incorporates a silicon ring resonator linked to a vertical grating coupler. It was manufactured using a 0.18 µm standard CMOS process, rendering a homogeneous integration into other electrical/optical devices. The temperature variation was measured by monitoring the shift in the resonant wavelength of the silicon resonator, which was induced by the thermo-optic effect and the thermal expansion effect. The dependence of its sensing capability upon the waveguide width of the resonator was intensively probed both theoretically and experimentally. The best achieved sensitivity was about 83 pm/°C for a waveguide width of 500 nm, while the sensitivity was boosted by ~10 pm/°C by adjusting the waveguide width from 300 nm to 500 nm. Finally, the response speed of the sensor was as fast as ~6 µs.

Refractometric sensor utilizing a vertically coupled polymeric microdisk resonator incorporating a high refractive index overlay.

A refractometric sensor resorting to a vertically coupled polymeric microdisk resonator was demonstrated, estimating the refractive index (RI) of an analyte by monitoring the resonant wavelength shift in its transfer characteristics. The disk resonator was especially overlaid with a high RI TiO2 film, thereby reinforcing the interaction of the evanescent field of its guided mode with the analyte. The sensitivity of the sensor was theoretically and experimentally confirmed to be enhanced by adjusting the overlay thickness. The fabricated sensor provided the maximum sensitivity of approximately 294 nm/RIU (refractive index unit) with the 40-nm-thick overlay, which is equivalent to an improvement of 150% compared with the case without the overlay.