A biophotonics catheter was conceived with collimation optics, an axicon lens, and custom design imaging optics
yielding a 360 degree scan aimed at imaging within concave structures such as arteries and lung lobes. The large depth
of focus is necessary to image a long-depth-range sample with constant transverse resolution in optical coherence
tomography (OCT). There are two approaches to achieving constant invariant resolution in OCT: Dynamic focusing or
Bessel beam formation. This paper focuses on imaging with Bessel beams. The Bessel beams may be created with
axicon optics which can be used instead of a conventional focusing lens in the sample arm of the OCT interferometer.
In this paper we present the design of a 2mm catheter for optical coherence endoscopy with resolution of about 5
micron across a depth of focus of about 1.6mm. Importantly, we investigated the fabrication of a 800μm diameter
axicon lens and the associated lateral resolution obtained over a long depth range in our OCT system, compared to the
same OCT system using a conventional lens.
Recently, Fourier domain optical coherence tomography (FDOCT) has attracted much attention due to the significantly improved sensitivity and imaging speed compared to time domain OCT. The large depth of focus is necessary to image a long-depth-range sample with constant transverse resolution in FDOCT where dynamic focusing is not considered. Under such imaging scheme, an axicon lens can be used instead of a conventional focusing lens in the sample arm of OCT to achieve both high lateral resolution and a long depth of focus simultaneously. In this study, a 800μm diameter axicon lens was fabricated on a silica wafer. We incorporated the fabricated axicon lens into the sample arm of our FD OCT system and investigated the lateral resolution over a long depth range, compared to the same FD OCT system using a conventional lens.
Graded index fiber has a limited bandwidth due to defects introduced in the fiber manufacturing process. In this paper, an alternative launch technique is presented using a diffractive element to excite specific modes in a fiber to maximize the bandwidth of graded index fiber.
Most laser projectors for LADAR systems are limited to small scan angles as they utilize acousto-optic devices, spatial light modulators, or fine-steering mirrors for beam steering. Additionally, the projected beam is usually circular and Gaussian. In order to improve the functionality of such systems, MEMS-based mirrors and diffractive optics may be used. This paper describes Digital Optics Corporation's work in developing and demonstrating a novel LADAR scanning system that incorporates a MEMS scanning mirror coupled with diffractive optical elements in a compact breadboard system. The MedCam MEMS mirror has been demonstrated with a 2D scan mode across large scan angles. The MEMS mirror system is experimentally compared to a Liquid Crystal Spatial Light Modulator based system. The diffractive elements generate spot arrays or other patterns that are more conductive to target detection schemes that an ordinary gaussian beam shape.
Standard laser welding practices are limited by the intensity profile of the beam and spot size. The introduction of Diffractive Optical Elements (DOE) to the welding process allows for new beam shapes that are better suited to the welding process. A particular problem in laser welding is the joining of dissimilar materials. Because these materials have different material properties including different melting temperatures, it is difficult to synchronize the welding process using a single spot. Additionally, significant thermal stresses are introduced by the welding process because of the keyhole weld shape formed by a gaussian beam. By using a power splitting DOE, two spots of unequal intensity distributions may be projected onto each side of the weld joint. This paper discusses the use of DOEs in laser welding and joining of dissimilar materials. Results are presented from the testing of several candidate aerospace materials.
Previously, a method of incorporating a microlens within a standard fiber optic ferrule was described. In this paper, the micro-rod and wafer fabrication concepts are explained, the wafer mapping/layout processes used to create the microlens substrate are detailed, and packaging in standard ferrules and v-grooves are described along with coupling results.
Silicon v-groove structures have been utilized for passive positioning of optical fiber for fiber optic and opto- electronic applications. In this paper, we will present our results of using micro-machined silicon v-groove arrays to passively align optical fiber arrays to micro rod optics. We will also demonstrate the integration of N fiber arrays bonded into the silicon v-groove with a 1xN micro lens array, which is composed of a 2 inch-phase level diffractive optics. For the assembly of 1x6 fiber array and lens array with 16 phase level diffractive optics, the experimental results indicated that total insertion loss per link is typically 1.5-2.0 dB/channel.
Optical connectors utilize microlens elements for coupling light into and out of fibers. Typically, these lenses are based on sapphire ball lenses or Gradient Index lens elements.However, lenses that are on the same scale as the single-mode fiber itself have not been previously realized. This paper introduces an optical lens element that fits into the single-mode optical ferrule, without any modifications to the connector package. This approach offers substantial performance and cost benefits over other methods.Both theoretical and experimental results are presented.