This paper is the first in a series of publications to investigate the use of commercial-off-the-shelf (COTS) components
for space flight fiber laser transmitter systems and LIDAR (laser imaging detection and ranging) detection systems. In
the current study, a hermetically sealed COTS LiNbO3 optical modulator is characterized for space flight applications.
The modulator investigated was part of the family of "High-Extinction Ratio Modulators" with part number MXPE-LN
from Photline Technologies in Besancon, France. Device performance was monitored during exposure to a Cobalt60
gamma-ray source. Results from the testing show little change in device operation for a total accumulated dose of 52
We have developed optical fibers with a very thin Lithium Niobate Layer at the glass core
glass cladding boundary it is observed that the Lithium Niobate Cylinder Fibers have a
large strain induced light loss of about 2.12784 x 10-5 per kg per m. These fiber can be
used as strain sensors operating in an amplitude mode rather than in the phase detection
mode as is the case for strain sensors using standard Single Mode Fibers.
Light absorption spectrum measurements and the light intensity dependence of the light absorption spectrum of a fiber with a very thin gold film at the glass core glass cladding boundary are presented. The thickness of the gold film is less than the scattering length of electrons in this metal. The absorption spectrum appears to be strongly light intensity dependent. We also observed the mode structure of light propagating through the gold film. Our fabrication process can produce large area very thin metal films that are very difficult to produce by other methods.
A MOEMS fiber modulator/sensor is fabricated by depositing a lithium niobate sol-gel thin film between the core and cladding of a fiber preform. The preform is then drawn into 125-µm fibers. Such a MOEMS modulator design is expected to enhance existing lithium niobate undersea acousto-optic sound wave detectors. In our proposed version, the lithium niobate thin film alters the ordinary silica core/cladding boundary conditions such that, when a stress or strain is applied to the fiber, the core light confinement factor changes, leading to modulation of fiber light transmission. Test results of the lithium niobate embedded fiber with a 1550-nm, 4-mW laser source revealed a reduction in light transmission with applied tension. As a comparison, using the same laser source, an ordinary silica core/cladding fiber did not exhibit any reduction in transmitted light when the same strain was applied. Further experimental work and theoretical analysis is ongoing.
A theoretical analysis of the light absorption and gain mechanisms in a Cd3P2 Semiconductor Cylinder Fiber is presented. The results of these calculations are in good agreement with previously published experimental data. Cd3P2 has two direct energy gaps, which both influence the gain mechanism. Pump light can be used to reduce the absorption. Stronger pump light that generates more charge carriers will produce net gain (gain above absorption compensation). The fiber exhibits gain over a very wide light wavelength bandwidth.
We have measured a net gain of 19.5 dB in a 4 mm long piece of Cd3P2Semiconductor Cylinder Fiber (SCF) at a wavelength of 1550 nm. The fiber was pumped from the side with a 100 mW, 832 nm laser. Side pumping is very inefficient since only a small portion of the pump light is absorbed by the very thin, approximately 6.694 nm thick, semiconductor film. However, this pumping arrangement is very convenient and does not require wavelength sensitive input and output couplers. We also measured the absorption spectrum. The absorption spectrum is in good agreement with a theoretical model. The absorption spectrum exhibits a step due to the two direct energy gap conduction bands of the Cd3P2 semiconductor film.
An fiber modulator/sensor has been fabricated by depositing a lithium niobate sol-gel thin film between the core and cladding of a fiber preform. The preform is then drawn into 125 um fiber. The proposed design of lithium niobate cylinder fibers can enhance the existing methdology for detecting sound waves under water utilizing the acoustooptic properties of lithium niobate. Upon application of a stress or strain, light propagating inside the core, acording to the principle of total internal reflection, escapes into the cladding because of the photoelastic boundary layer of lithium niobate. Test results of the lithium niobate fiber reveal a reduction in the 1550 nm, 4 mW source with applied tension. The source power from an ordinary quartz fiber under the same stress condition remained invariant to applied tension.
Nonlinear fiber optics, in the form of stimulated Brillouin scattering (SBS), has now emerged as the essential means for the construction of active optical devices used for all-optic in-line switching, channel selection, amplification, oscillation in optical communications, optical logic elements in optical computation and sensing, and a host of other applications. This paper attempts to present a survey and some of our own research findings on the nature of stimulated Brillouin scattering in single mode optical fibers and its device applications. In theory, the backscattering nature of the phenomenon enables its application as channel selectors and switches and filters in optical transmission and communications. We have been engaged in the design and implementation of fiber configurations, such as rings and loop mirrors, with the purpose of lowering the threshold. We report on experimental schemes involving Brillouin ring with amplifier-in-the ring, and Brillouin-NALMs (nonlinear amplifying loop mirrors). These successful devices are being studied for application as optical logic and neuron elements, Brillouin-NALMs for optical switching, and highly versatile sensors.