High-contrast spatial light modulator by use of the electroabsorption and the electro-optic effects in a GaAs single crystal

Abstract

A new spatial light modulator that uses the electroabsorption and the electro-optic effects in a GaAs single crystal is proposed. The device has the same structure as a Pockels readout optical modulator and can be operated at a frame rate higher than 500 Hz. When the electroabsorption and the electro-optic effects are combined, the dynamic range (contrast ratio) becomes larger than that which results when either effect is used singly. It was experimentally confirmed that the modulator has a high contrast ratio (greater than 2000:1), high sensitivity, and consequently large gamma characteristics.

Optical Properties of Multiferroic BiFeO3 Films

“…To determine the optical band gap, we plot (αE) 2 vs. E for the polycrystalline BFO film, as shown in Fig. 16(a), where α and E are the absorption coefficient and photon energy, respectively.…”

A review of active optical devices: I. Amplitude modulation

“…Currently, electroabsorbing devices with up to 800 × 800 pixels have been reported [27] with high fill factors (80-100%) and relatively low resolutions of 17-50 lp mm −1 . A photosensitivity of 240 µW cm −2 [24] has been reported in some devices that can be addressed optically.…”

“…On the other hand, in the Franz-Keldysh effect the application of an electric field bends the band diagram, thus reducing the effective band-gap and altering the levels of absorption at certain wavelengths. These types of electroabsorption devices can have a transmission variation of 41-0.4% [24] or contrast ratios of 300:1 [25] at 850 nm or 1550 nm with no polarization dependence. They are usually produced out of GaAs with a refractive index of 3.6.…”

“…Franz-Keldysh devices require an electric field of about 0-80 kV cm −1 , while Stark devices require a voltage of less than 30 V using currents that are less than 0.3 pA µm −2 . Stark devices, on the other hand, are faster than Franz-Keldysh devices as their reported frame rates go up to 15 MHz [26], while Franz-Keldysh devices can go only up to the kHz range [24]. Memory has been reported in some devices with a stability period of 5 ms [27].…”

Low driving voltage spatial light modulator fabricated by ultrahigh-purity GaAs

“…A liquid-crystal light valve is usually used; however, it has a low contrast ratio and low speed. High contrast and high speed SLMs using 400 μm thick semi-insulating (SI) GaAs have been reported [1] with the extinction ratio of 20 dB at 2.4 kV based on EA effect.…”