We developed high frame-rate en face optical coherence tomography (OCT) system using KTa1-xNbxO3 (KTN) optical beam deflector. In the imaging system, the fast scanning was performed at 200 kHz by the KTN optical beam deflector, while the slow scanning was performed at 800 Hz by the galvanometer mirror. As a preliminary experiment, we succeeded in obtaining en face OCT images of human fingerprint with a frame rate of 800 fps. This is the highest frame-rate obtained using time-domain (TD) en face OCT imaging. The 3D-OCT image of sweat gland was also obtained by our imaging system.
For high-speed optical beam scanning, we developed a novel planar optical deflector using KTa1-xNbxO3 (KTN) crystals. When a KTN deflector is operated at high frequencies, heat generated by KTN causes a decrease in its relative dielectric constant, which limits the deflection angle at frequencies above 200 kHz. To overcome this problem, we decreased the thickness of KTN to reduce its capacitance because the heat it generates is proportional to its capacitance. We arranged the two electrodes on the same surface, whereas previously reported structures have each electrode on opposite surfaces. We successfully reduced KTN’s capacitance to 1/30 of that previously reported. The deflection angle of this novel structure at 700 kHz is 16.89 mrad, which is more than half of that at 100 kHz, while the deflection angle of previously reported thick KTN rapidly decreases at more than 200 kHz. The experimental results indicate that our proposed planar optical deflector is effective for suppressing heat generation in KTN and improving the scanning speed of deflectors.
We have developed a wavelength-swept laser source with ultrahigh phase stability. Potassium tantalate niobate (KTa1-
xNbxO3, KTN) single crystal was employed as an electro-optic deflector for a high-speed wavelength sweep in the laser
cavity. A 200-kHz sweep rate was obtained with an average output power of 20 mW and a coherence length of 8 mm at
the wavelength range exceeding 100 nm. Since the electro-optic effect in KTN crystal has a fast response of more than
500 MHz, the deflection of a KTN deflector can follow the applied voltage precisely. Considering this advantage, we
demonstrated a swept source with ultrahigh phase stability in the 1.3 μm wavelength range as a result of the low-jitter
operation of the deflector. The standard deviation of measured timing jitters between adjacent A-lines was confirmed to
be less than 78 ps, which corresponds to a phase difference of 0.017 radians at a path difference of 1.5 mm of a
Michelson interferometer. The phase stability can be increased with an improved voltage source because the timing jitter
is still mainly caused by the voltage applied to KTN. In addition to realizing the phase stability of neighboring A-lines,
the long-term stable sweep was demonstrated by eliminating the refresh operation that was previously needed to prevent
output power decay. The ultrahigh phase stability we achieved makes our swept source promising for Doppler OCT and
polarization-sensitive OCT.
We propose a novel mechanical splicer that employs stripping-free fiber connection, which achieves a low connection
loss and a short assembly time. We also demonstrate single mode fiber connection with an average loss of 0.2 dB.
Intensive research on optical interconnections has attracted considerable attention for high-end router and server
applications. A polymer film waveguide is expected to be applied to an optical circuit board in an optical
interconnection. The film waveguide requires a conventional connector if it is to be employed as a practical optical
circuit board. This paper describes the MT connector used with polymer film waveguide (PMT connector), which is
compatible with the MT connector used with optical fiber. This connector can be attached to a film waveguide by
passive alignment, and is used to connect waveguides. When the connector was equipped with an epoxy resin film
waveguide, the insertion and connection losses were less than 1.4 and 0.5 dB, respectively. These losses are sufficiently
small to meet the basic requirement for optical circuit boards, so we were able to fabricate a flexible optical circuit board
with PMT connectors. This paper also describes the application of a film waveguide with PMT connectors to an optical
front plane system.
Intensive research on optical interconnection over flexible optical circuit boards has been undertaken for such applications as high-end routers, servers and cellular phones. And these flexible optical circuit boards are expected to be used for polymer optical waveguides. This paper reports recent progress on polymer optical waveguides. It also describes a flexible stamping method, which employs a flexible film stamp made of polymeric materials. Unlike conventional hard stamps, the flexible film stamp does not require either the stamp or its substrate to be perfectly flat, which means large area stamping is easy to achieve at reduced cost. We confirmed this by replicating 50 μm multi-mode optical polymer waveguides. The propagation loss of the waveguide is fairly low at 0.06 dB/cm at a wavelength of 850 nm. This loss is sufficiently small to meet the basic requirement for optical circuit boards, and the waveguide was used to fabricate a flexible optical circuit board with MT connectors.
Organic electroluminescent diodes (OLED) were fabricated on a polymeric optical waveguide for use as an optical interconnector in data communication systems. The OLED were fabricated on an ITO sputtered polymer waveguide with a 45 degree mirror by vacuum deposition. The OLEDs, with an emission peak center at 520 nm consist of diamine derivative as a hole transporting layer and tris(8-hydroxyquinoline) aluminum (Alq3) as an emissive layer. We estimated the propagation losses of the waveguide to be 1.35 dB/cm at 520 nm. However, it decreases as increasing the wavelength of the light source and is estimated as 0.37 dB/cm at the wavelength of 614 nm. The optical pulse of more than 5 Mb/s has been obtained from the OLED with Alq3 and diamine derivative. We discuss the properties of the OLED for the light source for polymeric integrated devices.
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