Search

There is a growing need for optical isolators that do not require a magnetic field, especially for uses such as on-chip optical devices and cold atom physics. As one approach, we propose using waveguides in photorefractive materials, such as F e : L i N b O 3 , as optical isolator devices due to their unique asymmetric transmission properties that allow low loss transmission in one crystal orientation and attenuation in the flipped orientation. We utilize ultrafast laser inscription to fabricate photorefractive depressed cladding waveguides in F e : L i N b O 3 along the crystal c axis to demonstrate the operation of F e : L i N b O 3 waveguide optical isolators. We show the ability to write transmission and reflection gratings into these waveguides that provide an isolation ratio of approximately 5000:1 per cm of path length.

HPCVD ZnSe optical fibers support hundreds to thousands of modes because they lack an appropriate cladding layer. Here, we demonstrate HPCVD deposited ZnSxSe1–x claddings to tune the number of supported modes.

Today fiber lasers in the visible to near-infrared region of the spectrum are well known, however mid-infrared fiber lasers have only recently approached the same commercial availability and power output. There has been a push to fabricate optical fiber lasers out of crystalline materials which have superior mid-IR performance and the ability to directly generate mid-IR light. However, these materials cannot currently be fabricated into an optical fiber via traditional means. We have used high pressure chemical vapor deposition (HPCVD) to deposit Fe

We utilize ultra-fast laser inscription to fabricate photorefractive type III waveguides in Fe:LiNbO3 along the crystal c-axis. We demonstrate the ability to write transmission and reflection gratings into these waveguides with losses of 2.5 dB cm-1 and 48 dB cm-1 respectively.

Ultrafast laser inscription (ULI) is a highly versatile technique for creating index modifications in glasses and crystalline materials. The process of ULI relies on ultrashort laser pulses focused inside of a material. The high intensity of the pulsed beam induces nonlinear absorption processes, which transfers the pulse energy to the material lattice. With careful experimental control of the laser parameters, a permanent change in the refractive can be obtained in the bulk material. The permanent refractive index change obtained by ULI can be used to create waveguides and devices in active and passive materials. In this work, we present recent advances on creation of guided wave devices in Mid-IR compatable materials such as Fe:ZnSe, Cr:ZnSe, Ho:YAG, LiNbO 3 , and CdSiP 2 .

High pressure chemical vapor deposition (HPCVD) has shown to be a promising method for producing Cr2+:ZnSe and Fe2+:ZnSe mid-IR optical fiber lasers. The oxidation state of the dopants and their spatial homogeneity are critical for the characterization of effective fiber laser performance; however, this is challenging for small fiber cores and small doping concentrations. We demonstrate using synchrotron micro X-ray fluorescence (XRF) mapping to study the distribution of the dopants throughout the fiber cross-sections. Furthermore, we study the local chemical environment of these unique fiber structures using micro X-ray near edge absorption spectroscopy (XANES). Our study reveals that transition metal doped ZnSe deposited using HPCVD has nanoscale dopant aggregation although the material is chemically identical to the commercially produced diffusion doped laser crystals, as indicated by the presence +2 oxidation state of the dopants. This work demonstrates the power of synchrotron-based X-ray techniques for use as metrology tools for improving the performance of laser materials in fiber geometry.

Polycrystalline zinc selenide optical fibers and fiber lasers are expected to provide powerful capabilities for infrared waveguiding and laser technology. High pressure chemical vapor deposition, which is the only technique currently capable of producing zinc selenide optical fibers, leaves a geometric imperfection in the form of a central pore which is detrimental to mode quality. Chemical vapor transport with large temperature and pressure gradients not only fills this central pore but also encourages polycrystalline grain growth. Increased grain size and a reduction in defects such as twinning are demonstrated with transmission electron microscopy, Raman spectroscopy, and X-ray diffraction, supporting that high-quality material is produced from this method. Finally, the mode structure of the waveguide is improved allowing most of the guided optical intensity to be centrally positioned in the fiber core. Loss as low as 0.22 dB/cm at 1908nm is demonstrated as a result of the material improvement.

Today fiber lasers in the visible to near-infrared region of the spectrum are well known, however mid-infrared fiber lasers have only recently approached the same commercial availability and power output. There has been a push to fabricate optical fiber lasers out of crystalline materials which have superior mid-IR performance and the ability to directly generate mid-IR light. However, these materials cannot currently be fabricated into an optical fiber via traditional means. We have used high pressure chemical vapor deposition (HPCVD) to deposit Fe2+:ZnSe into a silica optical fiber template. These deposited structures have been found to exhibit laser threshold behavior and emit CW mid-IR laser light with a central wavelength of 4.12 µm. This is the first reported solid state fiber laser with direct laser emission generated beyond 4 µm and represents a new frontier of possibility in mid-IR laser development.

Semiconductor optical fibers encapsulated in a protective diamond coating can theoretically lead to immense power handling capabilities and infrared functionality. Here, silicon optical fibers are grown using high pressure chemical vapor deposition before being coated by 50 μm–300 μm of diamond by microwave plasma-assisted chemical vapor deposition. This coating extends conformally around the fiber cross section with diamond crystallites in the film on the order of several micrometers. Complete coating of high-quality diamond around the fiber is indicated by scanning electron microscopy and Raman measurements. The encapsulated silicon fibers are durable enough to survive the diamond deposition process, as demonstrated by their ability to guide infrared light.

Popcorn, one of the most popular snack foods in the world, is known for being a high fiber, healthy food. Our research has found that commercial popcorn also contains significant amounts of the class of antioxidants known as phenolic acids. The total antioxidant power of raw and popped popcorn extract has been quantified using the Folin-Ciocalteu and FRAP assays. The polyphenols were found exclusively in the pericarp of the kernel completely bound to the oligosaccharide fiber matrix. An in vitro digestion study was also performed to predict the phenolic acids’ bioavailability. On average, nine commercial popcorn samples contain 5.93 ± 0.92 mg/g of total polyphenols after alkaline hydrolysis and 2.66 ± 0.15 mg/g after in vitro digestion as measured by the Folin-Ciocalteu assay. Furthermore, the popping process was found not to significantly decrease the antioxidant capacity. These results indicate that a considerable amount of the bound polyphenols are bioaccessible. Due to the high levels of bioaccessible polyphenols, popcorn may be a significant source of dietary polyphenol antioxidants.

The purpose of this study was to analyze polyphenol rich beverages (vitamin enhanced waters (VEWs), fruit juices and berry juices) to determine free polyphenol concentrations and free polyphenols per Calorie based on a serving size. The Folin-Ciocalteu reagent was used in a colorimetric assay based on a catechin standard. Fruit and berry juices contained, on average, more than eight-times the concentration of free polyphenols when compared to VEWs. When Calories per serving were taken into consideration, fruit and berry juices contained more than twice the free polyphenols per Calorie.

To date, efforts to power scale Cr2+:ZnSe gain media have been limited by its high thermo-optic coefficient. We demonstrate the first continuous wave Cr2+:ZnSe fiber lasers, providing a path forward for high power systems.

Though much attention has been devoted to phenolics in beans, to our knowledge no studies have been done to determine the effect commercial canning has on these compounds. Free and total phenolic concentration in 18 cultivars of raw beans and 9 cultivars of commercial canned beans was determined. Alkaline hydrolysis was used on samples prior to analysis by Folin-Ciocalteu's reagent (FCR) and ferric-reducing antioxidant power (FRAP). A correction for non-phenolic antioxidants, interferences, was then made. There is a significant difference between the free phenolics of canned and raw beans using FCR (P = 0.006) but not FRAP. There is also a significant difference in the total phenolics of canned and raw beans using FRAP (P = 0.006) but not FCR. When considered on a single serving basis, the amount of phenolics in canned beans is comparable to that provided by raw fruits and vegetables.