ABSTRACT
In this Letter, we reported anomalous electro-optic potassium tantalate niobate (KTN) devices, in which both electrons and holes were injected into the KTN crystal via ultraviolet (UV) illumination-assisted charge injection. This could not only significantly enhance the performance of electro-optic devices (e.g., a 270% increase in the deflection angle in terms of the KTN deflector) but also enable the new bi-directional scanning capability. The results in this work would be very useful for a variety of devices and applications, such as electro-optic based vari-focal lenses.
ABSTRACT
Spatially analyzing non-uniform distributions of electric phenomena such as electric field and permittivity in ferroelectric devices is very challenging. In this study, we apply an optical beam deflection method to map the non-uniform electric phenomena in relaxor ferroelectric potassium tantalate niobate (KTN) crystals. To adequately correlate the physical parameters and their spatial distributions in KTN crystals, a general model that describes the giant electro-optic response and associated beam deflection is derived. The proposed model is in good agreement with the experimental results and is envisioned to be useful for analyzing electric field-induced phenomena in non-linear dielectric materials and devices.
ABSTRACT
Most applications of a ferroelectric-based electro-optic (EO) beam deflector have been limited by the high applied voltage. In this Letter, we report a dramatically increased EO beam deflection in relaxor ferroelectric potassium tantalate niobate (KTN) crystals by using the electric-field-enhanced permittivity. Due to the existence of the electric-field-induced phase transition in relaxor ferroelectric materials, the dielectric permittivity can be substantially increased by the applied electric field at a certain temperature. Both the theoretical study and the experimental verifications on the enhanced beam deflection and EO effect in the case with the electric-field-induced high permittivity were conducted. The experimental results confirmed that there was a three-fold increase in the deflection angle, which represented a dramatic increase in the deflection angle. By offering a wider deflection range and a lower driving voltage, such a largely enhanced beam deflection is of great benefit to the KTN deflector.
ABSTRACT
This publisher's note contains corrections to Opt. Lett.44, 5557 (2019)OPLEDP0146-959210.1364/OL.44.005557.
ABSTRACT
We report a new type of photoconductive semiconductor switch (PCSS), consisting of a semi-insulating gallium arsenic (GaAs) substrate and a front-bonded ruby crystal. The 532 nm laser pulses from an Nd-YAG laser incident on the front surface of the ruby crystal. A portion of the laser pulse passes through the crystal and reaches the GaAs substrate, and the remaining portion of the laser pulse is absorbed by the ruby crystal. This results in the emission of 694 nm fluorescent light. Furthermore, a portion of emitted fluorescent light also reaches the GaAs substrate. The high-fluence 532 nm short laser pulse with a pulse width around several nanoseconds is used to trigger the PCSS entering the high-gain nonlinear mode, whereas the low-fluence long-lifetime (on the order of a millisecond) 694 nm fluorescent light is used to maintain the lock-on time. Thus, an ultralong lock-on time on the order of millisecond is achieved, which is 3 orders of magnitude longer than a typical lock-on time of high-gain GaAs PCSS.
ABSTRACT
In this paper, a high-speed non-mechanical two-dimensional KTN beam deflector is reported. The scanning mechanism is based on the combination of space charge controlled beam deflection and temperature gradient enabled beam deflection in a nanodisordered KTN crystal. Both theoretical analyses and experimental investigations are provided, which agree relatively well with each other. This work provides an effective way for realizing multi-dimensional high-speed non-mechanical beam deflection, which can be very useful for a variety of applications, including high-speed 3D laser printing, high resolution high speed scanning imaging, and free space reconfigurable laser communications.
ABSTRACT
In this paper, we report a three orders-of-magnitude increase in the speed of a space-charge-controlled KTN beam deflector achieved by eliminating the electric field-induced phase transition (EFIPT) in a nanodisordered KTN crystal. Previously, to maximize the electro-optic effect, a KTN beam deflector was operated at a temperature slightly above the Curie temperature. The electric field could cause the KTN to undergo a phase transition from the paraelectric phase to the ferroelectric phase at this temperature, which causes the deflector to operate in the linear electro-optic regime. Since the deflection angle of the deflector is proportional to the space charge distribution but not the magnitude of the applied electric field, the scanning speed of the beam deflector is limited by the electron mobility within the KTN crystal. To overcome this speed limitation caused by the EFIPT, we propose to operate the deflector at a temperature above the critical end point. This results in a significant increase in the scanning speed from the microsecond to nanosecond regime, which represents a major technological advance in the field of fast speed beam scanners. This can be highly beneficial for many applications including high-speed imaging, broadband optical communications, and ultrafast laser display and printing.
