We present the basic characteristics of amplitude modulation cantilever with optical waveguide in liquid. This optical waveguide cantilever-based transducer can be used for small particle detection or biological sensing in liquid environments. Essentially, the SiON waveguide embedded in the SiO2 cantilever is designed and fabricated to detect the biomolecular interaction or small particle in the liquid. For a measurement, the actuation based on amplitude modulation is applied for a stable oscillation of the cantilever in liquid environment. Finally, modulated output signal of optical waveguide cantilever were measured and analyzed.
We propose a cost effective digitized radio-over-fiber (D-RoF) system employing a sigma delta modulation (SDM) and a bidirectional transmission technique using phase modulated downlink and intensity modulated uplink. SDM is transparent to different radio access technologies and modulation formats, and more suitable for a downlink of wireless system because a digital to analog converter (DAC) can be avoided at the base station (BS). Also, Central station and BS share the same light source by using a phase modulation for the downlink and an intensity modulation for the uplink transmission. Avoiding DACs and light sources have advantages in terms of cost reduction, power consumption, and compatibility with conventional wireless network structure.
We have designed a cost effective bidirectional D-RoF system using a low pass SDM and measured the downlink and uplink transmission performance in terms of error vector magnitude, signal spectra, and constellations, which are based on the 10MHz LTE 64-QAM standard.
A silicon optical modulator operating at high speed and low voltage is proposed by using a Schottky diode. The optical modulation is achieved by the intensity change of guiding light due to free-carrier absorption, not conventional interference effects. The rib waveguide structure of the modulator has a height of 340 nm, a etch depth of 150 nm, a width of 4.8 μm, and a modulation length of 500 μm. It was designed to maximize the free carrier injection by a Schottky contact on the rib waveguide center. The center of the rib waveguide is lightly doped with phosphorus of 1016 cm−3, and the sides are heavily doped with phosphorus of 1020 cm−3 to improve modulation depth by injecting free carriers into the center of the rib waveguide. This design allowed a high overlap between the optical mode and carrier density variations in the center of the waveguide. To achieve high speed operation, travelling-wave type electrodes were designed to allow co-propagation of electrical and optical signals along the waveguide. The device simulated results demonstrate a 3.3 dB modulation depth for a 500 μm modulation length with 3 Vpp driving voltages. We demonstrated a Schottky modulator operating Si EAM at 3 Vpp with a 3 dB bandwidth of 7 GHz.
New conceptual display structure is introduced by using TIR characteristics and BPLC as alight shutter. In our structure,
non-polarized light source can be used as incident light due to the isotropic characteristics of BPLC unlike previously
suggested waveguide display concept using nematic LC at '0' bias voltage. In addition, light leakage in the case of
BPLC is smaller than that in the case of nematic LC. According to the wave mode, TM mode or TE mode, the critical
angle is different from each other due to homeotropical characteristics of BPLC at bias voltage. Then, each critical angle
is measured and optoelectronic characteristics of BPLC are estimated with increasing applied voltage. In addition, the
intensity characteristics according to bias voltage across BPLC are studied with various waves. We confirm the nonpolarized
light source can be automatically filtered, and directly used for waveguide display by BPLC. Consequently,
BPLC can be nominated as a new light shutter in waveguide display structure using TIR mechanism.