Abstract
The doubly periodic Si photonic crystal waveguide radiates the guided slow light into free space as an optical beam. The waveguide also functions as a beam steering device, in which the steering angle is changed substantially by a slight variation in the wavelength generated due to the large angular dispersion of the slow light. A similar function is obtained when the wavelength is fixed and the refractive index of the waveguide is changed. In this study, we tested two kinds of integrated heater structures and observed the beam steering using the thermo-optic effect. For a p-i-p doped waveguide, the heating current was made to flow directly across the waveguide and a beam steering range of 21° was obtained with a relatively low heating power and high-speed response of the order of 100 kHz, maintaining a narrow beam divergence of 0.1-0.3° and a 120 resolution points. We also performed a preliminary life test of the device but did not observe any severe degradation in the temperature variation of 80-430 K for the duration up to 20‒40 h. For a TiN heater device, we obtained the comparable beam steering characteristics, but the required heating power increased, and the response speed decreased drastically.
Highlights
Optical beam steering devices that orient an optical beam toward a target are crucial components in the manufacturing of devices such as printers, copiers, laser displays, laser processors, security sensors, and light detection and ranging (LiDAR) systems, among others
The waveguide functions as a beam steering device, in which the steering angle is changed substantially by a slight variation in the wavelength generated due to the large angular dispersion of the slow light
Funding Accelerated Innovation Research Initiative Turning Top Science and Ideas into High-Impact Values (ACCEL); Japan Science and Technology Agency (JST) (JPMJAC1603)
Summary
Optical beam steering devices that orient an optical beam toward a target are crucial components in the manufacturing of devices such as printers, copiers, laser displays, laser processors, security sensors, and light detection and ranging (LiDAR) systems, among others. It is difficult to simultaneously achieve a high speed and sharp optical beam, which can be obtained by a reasonably large mirror, such as, a mirror with a diameter of several millimeters These days, optical phased arrays (OPAs) and waveguide diffraction gratings fabricated by the Si photonics CMOS process are being studied extensively as such nonmechanical devices. We have proposed a slow-light beam steering device that uses photonic crystal waveguide (PCW) with a surface diffraction grating [9]. We achieved ∆θ = 23° for a wavelength sweep range (Δλ) of 20 nm by using a similar device, but this device had a doubly periodic photonic crystal pattern instead of the surface grating [11].
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