We comparatively studied laser performance in the mixed vanadate crystals Nd:YxGd1-xVO4 with direct and indirect pumping. The maximum CW output power at 1064 nm was measured to be 6.6 W with 12 W direct 880 nm laser diode pumping, and 4.4 W with 8.8 W indirect 808 nm pumping. The optical conversion efficiency depended on the mixture ratio (x), pumping wavelength (direct or indirect), and pumping power. The hightest optical efficiency of 59% and slope efficiency of 74% were achived.
We present, for the first time, comparative studies of laser performance in the mixed vanadate crystals Nd:YxGd1−xVO4 with direct and indirect pumping. A series of mixed vanadate crystals Nd:YxGd1−xVO4 with different yttrium and gadolinium composition ratios but the same Nd3+ dopant level is prepared under the same fabrication processes and their laser performance in the TEM00 mode operation is studied using the same experimental configuration under direct pumping with laser diodes at 880 nm as well as indirect pumping at 808 nm. Remarkable improvement in laser efficiency and maximum achievable output power is achieved under direct 880-nm excitation over indirect 808-nm excitation. The maximum optical slope efficiency in the TEM00 mode operation is 74% with direct 880-nm pumping, which also produces the maximum overall optical-to-optical conversion efficiency of 59%. The maximum attainable laser power is up to 50% higher under direct 880-nm pumping over the more conventional 808-nm pumping. These achieved results provide valuable insight into crystal composition selection and pump schemes for the mixed vanadate crystals, which have the potential to tailor laser parameters through crystal composition engineering.
We present, for the first time, comparative studies of laser performance in the mixed vanadate crystals
Nd:YxGd1-xVO4 with direct and indirect pumping. The resulting highly efficient miniaturized laser has potential for laser
communications.
We report a new type of high-speed electro-optic (E-O) beam scanner based on Potassium Tantalate Niobate
(KTN) crystal. It has larger scanning angle, better angular resolution, and lower driving voltage comparing to the
traditional E-O crystal beam scanner. Compared to conventional moving mirrors such as servo-controlled mirrors and
galvanic mirrors, the demonstrated E-O beam scanner can improve the response time by 100 times. The presented
device has many other unique features such as light weight, small dimension, low power consumption, and no-moving
components particularly suitable for airborne and space-borne applications.
This paper provides research progress in the development of fast electro-optic gratings based on liquid crystals for laser beam attenuations. The electro-optic phase grating is formed by the phase
separation of ~100nm liquid crystals droplets from a polymerizing organic matrix using holographic interference technique. The formed grating separates the incident laser beam into the output beams: the transmitted and diffracted beam, whose intensities can be electrically adjusted through electro-optic effect. The fast
electro-optic gratings have a very fast electro-optic response time of 50 microseconds with diffraction efficiency above 99.8%. Optical receivers used in FSO have a limited dynamic range and there is a need for in-line variable attenuators to keep the signal levels from overloading the receiver. These attenuators should be continuous,
provide sufficient attenuation, and also provide a low insertion loss for weak signal reception. The use of electro-optic Bragg gratings is one solution to meet the requirements for an in-line attenuator for FSO.
We present a novel high-speed electro-optic beam scanner that provides a
significantly improved scanning angle, angular resolution, and response time. Compared
to conventional moving mirrors such as servo-controlled mirrors and galvanic mirrors,
the demonstrated laser scanning device can improve the response time by 100 times. The
presented device has many other unique features such as light weight, small dimension,
low power consumption, and no-moving components, which are particularly suitable for
airborne and space-borne applications. Electro-optic beam scanners are key components
in advanced laser radars, laser communication systems. It also has important commercial
applications in various fields such as display, printing, imaging, optical storage, optical
communication, and so on.
This paper provides research progress in the development of fast electro-optic gratings for high energy laser
beam attenuations. The electro-optic phase grating is formed by the phase separation of small liquid crystals droplets
from a polymerizing organic matrix using holographic interference technique. The formed grating separates the incident
laser beam into two output beams: the transmitted and diffracted beam, whose intensities can be electrically adjusted
through electro-optic effect. The fast electro-optic gratings have a very fast electro-optic response time of 50 &mgr;s is with
diffraction efficiency above 99%.
With Gd ions replacing a fraction of Y ions in Nd:YVO4 crystal, a new class of mixed gadolinium yttrium vanadate crystals Nd:Y1-xGdxVO4 is formed with adjustable laser parameters. As a result, a new laser crystal may be produced with optimized stimulated cross-section and fluorescence lifetime. In this paper, important laser parameters, such as material thermal properties, laser slope efficiency, and overall optical-to-optical efficiency, of new mixed vanadate crystals Nd:Y1-xGdxVO4 were investigated with different Nd doping levels as well as different yttrium and gadolinium composition ratios. Comparative studies will be presented in reference to better known laser crystals like Nd:YVO4 and Nd:GdVO4 crystals.
We report a large aperture laser beam attenuator by using electrically switchable gratings. This attenuator separates an incident beam into the transmitted and diffracted beams. The light intensities of both transmitted and diffracted beams can be adjusted through electro-optical effect. By carefully selecting the liquid crystals and polymer materials, we obtained a 25 dB dynamic range of attenuation with a 0.5 dB insertion loss and response time about 200 μs.
A monolithically integrated high-speed true-time-delay line with embedded electrically switchable Bragg gratings was developed and characterized. Such a monolithically integrated device structure leads to a significantly reduced device size and allows a more precise RF phase control. A 40 ps reprogrammable optical true-time delay increment was acheived with a very fast switching speed of <50 µs.
A class of Nd-doped mix vanadate crystals Nd:YxGd1-xVO4 showed high potential in tailoring laser parameters for various applications with different Y and Gd composition ratios. Important thermal and thermo-optical properties, such as thermal conductivity and the temperature dependence of the index of refraction, were measured in these crystals along a-axis and c-axis. Results will be compared to well-known Nd:YAG, Nd:YVO4, and Nd:GdVO4 crystals.
We demonstrate a 4-bit optical true time-delay module for synthetic aperture radars based on the integration of polymer channel waveguide and electro-optic Bragg gratings. The demonstrated device is a truly integrated module that eliminates the most difficult packaging problem associated with the delicate interfaces between optical fibers and optical switches. The total insertion loss of the 4-bit optical true-time-delay line is less than 3 dB with switching time <50 □s and driving voltage of 25 V.
We demonstrate the first integration of polymer waveguides and electrically switchable gratings in a single substrate for the application of optical interconnect. The electrically switchable gratings are used to couple optical signals from VCSEL to waveguide or from waveguide to photodetector. This switchable coupling feature provides a promising solution to facilitate dynamically reconfigurable on-chip optical interconnect architecture for intrachip and chip-to-chip data communication.
We present an array of electro-optic Bragg gratings for on-chip optical waveguide interconnect applications. These electro-optical gratings can serve as switchable couplers to couple high-speed optical signals from a vertical cavity surface emitting lasers (VCSEL) to on-chip polymeric waveguides and from waveguides to photodetectors. The unique switching feature provides a promising solution to facilitate dynamically reconfigurable on-chip optical interconnects architecture for intra-chip, chip-to-chip and board-to-board data communications. We demonstrate on-chip switched optical waveguide interconnect using electro-optic grating and polymeric channel waveguides on a silicon substrate.
This paper provides a description of the research for the development of an integrated high speed true-time-delay module for synthetic aperture radars. The unique feature of the approach is that the true-time-delay waveguide circuit and electro-optic switching elements are integrated. As a result this integration significantly reduces the device size while simplifying the difficult packaging problem associated with the interfaces between optical fibers and optical switches. Such a monolithic approach provides greater precision for the RF phase control that the phase control provided by fiber-delay-lines as a result to the submicrometer accuracy of lithography-defined polymeric waveguides. More importantly, the optical switched true-time-delay network requires less electrical power due to the low power consumption of electrically-switchable waveguide gratings. Furthermore, the electrically-switchable waveguide gratings have a very fast switching speed (<50 μs) that is at least 100 time faster than any existing commercial optical switching matrix.
It has been realized that the lack of enabling technology of beam forming and steering devices significantly slows down the process of implementing wideband phased array antenna systems. In this paper, we present our research in developing an integrated electro-optic switched true-time-delay module as a boradband beam forming device for wideband phased array antennas. The unique feature of our approach is that both the true-time-delay waveguide circuit and electro-optic switching elements are monolithically integrated in a single substrate. As a result, this integration significantly reduces the device size while eliminating the most difficult packaging problem associated with the delicate interfaces between optical fibers and optical switches. Such a monolithic approach offers greater precision for the RF phase control than the fiber-delay-lines thanks to the sub-micrometer accuracy of lithography-defined polymeric waveguides. More important, the proposed optical switched true-time-delay network requires very low electrical power consumption due to the low power soncumption of electrically-switchable waveguide gratings. Furthermore, the electrically-switchable waveguide gratings have a very fast switching speed (<50 μm) that is at least 100 times faster than any existing commercial optical switching matrix. Photonic phased array antenna based on optical true-time delay lines offers improved performance and reduced weight and power consumption over existing parabolic dish antenna presently used for communications.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.