Based on a finite-conjugate objective lens with numerical aperture of 0.62 for a 650-nm wavelength, an optical pickup head composed of a multifunction beamsplitter and a diffractive optical element is designed be used in a swing-arm-type optical pickup head. The diffractive optical element is a lens with an elliptical four-level phase profile to provide both focusing and astigmatism. It is also designed with the goal to simplify the overall optical configuration and provide linear characteristics for the focus error signal.
This paper presents an optical head design that minimizes the component number and miniaturizes the head dimension
by using a novel reflective prism-type holographic optical element (PT-HOE) for the next-generation high-density bluelight
system with small form factor (SFF). The PT-HOE combines four functions, serving as a folding mirror, a beamsplitter,
an aberration correction element, and a servo-signal generation device, which are generally required for a
conventional optical pickup head (OPH). It greatly simplifies the system complication and assembly procedure of an
OPH. Simulations give the satisfactory results and show the feasibility for realizing a high-density SFF OPH with a
simple and compact configuration.
A pop-up binary-phase micrograting and a pop-up micro polarization beamsplitter, for potential use in micro-optical pickups, have been realized on a single silicon chip using a two-layer polysilicon and one-layer silicon nitride micromachining process. In the case of the micrograting, a diffraction efficiency ratio between 4 and 10 can be achieved provided that the duty cycle is between 0.4 and 0.6 and the depth between 455 and 485 nm, respectively. For a grating designed for a diffraction ratio of 7, the measured ratio is 8.31. The polarization beamsplitter is a silicon nitride thin film placed at the Brewster angle. The transmittance of the TM mode was measured to be more than 98.5%, while the reflectance of the TE mode was 21.4%.
The focusing objective lens is a key component in the optical pick-up head. In this paper, focused ion beam milling is used to fabricate a NA 0.65 microlens in the silicon nitride film suspended on a silicon substrate. The measured NA is 0.64 and the focused spot size is 0.64 μm.
A stress-induced curved \micro actuator with a grating attached at the end is demonstrated for recordable optical
storage applications. The actuator and the grating were fabricated using a two-layer poly-silicon and one-layer silicon
nitride micro-machining process. Three diffracted beams with equal intensity from the grating were generated when a
voltage is applied to the actuator to switch its position. The single-beam and multi-beam configurations can be used for
writing and reading data in the disc, respectively.
The design and fabrication of micro gratings and polarization beam splitters for potential use in micro optical pickups are presented. Silicon nitride is used as the optical material for its low absorption in the visible wavelength. The micro components are framed by a pop-up poly-silicon mechanism as in the standard surface micromachining technology.
The micro grating is a binary phase grating. The diffraction ratio between 4 and 10 can be achieved provided that the duty cycle is between 0.4 and 0.6 and the depth between 455nm and 485nm. For a grating designed for a diffraction ratio of 7, the measured ratio is 8.31.The polarizing beam splitter is a silicon nitride thin film placed at the Brewster angle. The transmittance of the TM mode of a micro polarization beam splitter was measured to be more than 98.50%.
As the recording density of longitudinal magnetic storage increases at a 100% annual growth rate, it will soon approach the superparamagnetic limit where the thermal energy at room temperature starts to induce thermal instability to the grains in the small recorded marks. Thermal magnetic recording schemes, such as those used in magneto-optical recording, help alleviate the problems with the superparamagnetic limit. Recently, a hybrid recording system was proposed where data were recorded thermal magnetically on a magneto-optical disk and read back with a GMR head. In this paper, we propose an integrated planar read that combines an optical fiber lens, a solid immersion lens, a sub wavelength aperture, a micro coil, an air bearing surface, and a GMR head for such a hybrid recording system. Preliminary fabrication and calculation are discussed.
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