UV Trimming Research Articles

Eight-channel silicon–silica hybrid thermo-optic switch with improved extinction ratio realised by UV trimming

An eight-channel thermo-optic switch with a low power consumption of 0.7 mW/channel, based on a silicon-silica hybrid structure, is described. The extinction ratio is improved from 3 dB to more than 15 dB by using birefringence control with an Ar ion laser trimming technique.

Origin of UV Sensitivity of SiON Film and Bidirectional UV Trimming of SiON Microring Resonator

We discovered a photoluminescence phenomenon of SiON waveguide by the UV irradiation and investigated the luminescence spectrum by a conventional microscope and diffraction grating spectroscopy. It was shown from these measurements that the defect created by UV irradiation causes the UV sensitivity of SiON film after thermal annealing. Next, we measured the spectrum change of a microring resonator with SiON core via single point long time UV irradiation and multi point UV irradiation. As a result, we demonstrated a selective UV trimming of microring resonator combining thermal annealing and multi point UV irradiation.

UV trimming of Polarization-independent Microring Resonator by Internal Stress and Temperature Control

The temperature dependence of the resonant wavelength of vertically coupled microring resonator can be controlled via internal stress caused by the thermo-optic and photo-elastic effects. In the case of strong internal stress, a polarization-independent microring resonator can be realized by controlling the device surface temperature using a heater module; the temperature dependence of TE and TM polarizations are different due to the internal stress and thus manipulating temperatures, the resonant wavelengths for TE and TM can be equalized at a specific temperature. In this study, the UV trimming of polarization-independent wavelength was demonstrated using UV-sensitive SiON as a core material. The temperature dependence of TE polarization was almost athermalized and that of TM was made negative by controlling internal stress. As a result, the simultaneous realization of the UV trimming and the polarization-independent microring was made possible more easily than before; the UV trimming can be done at room temperature due to the athermalized resonant wavelength for TE polarization.

Property improvement of flat-top 50GHz-88ch arrayed waveguide grating using phase correction waveguides

We have proposed a novel circuit design with the phase correction waveguides in part of the arrayed waveguides to improve the property of an AWG with a narrow spacing and a large channel count without the additional processes such as a UV trimming method. Employing this novel circuit design, we have successfully demonstrated a flat-top 50GHz-88ch with a low crosstalk experimentally.

Reversal of UV Sensitivity and Loss Reduction of SiON Microring Resonator by Thermal Annealing

To investigate the origin of the large UV sensitivity of SiON film, we measureed the Fourier transform infrared (FT-IR) spectrum of SiON films before and after UV exposure, and also before and after thermal annealing. As a result, we discovered the reversal of the UV sensitivity of SiON film treated by thermal annealing at 1160 °C. Next, the origin of the reversal of UV sensitivity induced by thermal annealing was studied by positron annihilation lifetime spectroscopy (PALS) measurement. The redshift trimming of a microring resonator with a SiON core and the improvement of a double series coupled microring resonator by selective UV trimming were successfully demonstrated using this phenomenon.

High UV Sensitivity of SiON Film and Its Application to Center Wavelength Trimming of Microring Resonator Filter

We demonstrated a vertically coupled microring resonator (VCMRR) filter as an Add/Drop wavelength filter. However, the accuracy of center wavelength was not sufficiently high for dense wavelength division multiplexing (DWDM) systems. Thus, a UV trimming technique using a SiN (n=2.01 at λ=1.55 μm) ring core was previously developed. Although a wide center wavelength trimming range of -12.1 nm and the long-term stability of center wavelength were realized, the core size required for single-mode propagation was too small for fabrication using a photolithography process. Therefore in this study, we introduced SiON as the microring core to relax the single-mode condition of core size. We discovered a large UV sensitivity of SiON film formed by a PECVD method, and a wide range UV trimming of microring resonator of -10.5nm was demonstrated using this phenomenon.

Influence of Bragg gratings phase mismatch in a Mach-Zehnder-based add-drop multiplexer

In this paper, the importance of Bragg gratings detuning in a Mach-Zehnder-based optical add-drop multiplexer is emphasized. This parameter has to be minimized to achieve a high-performance component in order to add, drop, or transmit dense-wavelength-division-multiplexed channels at the same time. The Bragg gratings phase mismatch influence on throughput isolation and on the backreflected signal spectral shape during UV trimming is also discussed.

Fiber Fabry-Perot interferometer with mode-converting Bragg gratings

Bragg gratings are genuine narrow band reflectors. However, for several applications narrow band transmission filters are of interest. It is demonstrated that a pair of mode-converting Bragg gratings in a Fabry-Perot interferometer configuration yields a nonreflecting, narrow-band transmission filter. A more detailed investigation shows further a different mode of operation where narrow band reflection occurs in resonance. It is shown experimentally how both modes of operation are attained by UV trimming of the Fabry-Perot interferometer. A mathematical model for the mode-converting Fabry-Perot interferometer is given.

UV trimming of fused fiber coupler spectral response: a complete model

In this letter, we propose a complete model of the transmission change of fused tapered fiber couplers exposed to uniform UV light by using supermode propagation theory. The main contribution of this change is found to be a decrease of the supermode propagation constant difference. This effect is found to be more significant when supermodes become cladding modes. The model shows a good qualitative agreement with experimental results found in the literature.

UV trimming of arrayed-waveguide grating wavelengthdivision demultiplexers

The transmission peak wavelength of a fibre-pigtailed arrayed-waveguide silica-on-silicon grating (AWG) demultiplexer has been shifted using a 248 nm excimer laser without penalties in crosstalk or insertion loss. The transmission peak shift and shape were monitored while trimming. A wavelength shift of 0.77 nm (94 GHz) was achieved while keeping a crosstalk of –25 dB for 400 GHz channel spacing and an insertion loss < 7 dB.

Integrated-optical Mach–Zehnder add–drop filter fabricated by a single UV-induced grating exposure

A four-port bandpass filter is demonstrated with good performance by use of UV-induced Bragg gratings in P-doped channel waveguides without UV trimming. The simple, single-step fabrication procedure is experimentally and theoretically analyzed, and tolerances are calculated for achieving practical wavelength-division-multiplexed communication system performance.

Highly stable optical add/drop multiplexer using polarization beam splitters and fiber Bragg gratings

We demonstrate a novel wavelength-division add/drop multiplexer employing fiber Bragg gratings and polarization beam splitters. The multiplexer is easy to fabricate without any special technique such as UV trimming, and yet shows very stable performance with less than 0.3-dB crosstalk power penalty in a 0.8-nm-spaced, 2.5-Gb/s-per-channel wavelength-division multiplexing (WDM) transmission system.

Laser Trim Revisited in the Light of an Excimer Laser

ABSTRACTIn the Laser Chemistry Group's program aimed at understanding the basic mechanisms involved in the fabrication and characterization of integrated circuits, we have converted an infrared laser-based, thick film trimming technique, which is over 15 years old, to UV light. It is known that excimer lasers can be used for microfabrication of semiconductors and ceramics. Much cleaner ablations than those obtainable with the infrared lasers have been demonstrated in a large variety of materials. This, together with the fact that excimers with repetition rates over 1 kHz are presently on the market, leads us to propose that better accuracies and smaller drifts, should be achievable using excimer laser-based thick film hybrid circuit trimming. Results of XeCl laser trimming of over four hundred resistors, including temperature coefficient of resistance measurements and life tests at elevated temperatures, demonstrate that UV trimming is a factor of 10 better than the presently used infrared process.