A development of microlenses achromatically corrected for near infrared range is reported. Internal nanostructurization of microlens allows to obtain an effective parabolic gradient index profile. A standard stack-and-draw method was used to fabricate the microlens. They have a nearly wavelength-independent working distance of 35 μm over the wavelength range of 600-1550 nm. The proposed achromatic microlens can be applied in micro imaging systems and for wavelength independent coupling into optical fibers.
Biocompatible optical waveguides receive increasing attention owing to their application potential in the biomedical field. Our focus is on the fabrication and characterization of a new step-index biodegradable polymer optical fiber (bioPOF) using two commercial polyesters: poly(D,L-lactic-co-glycolic acid) (PDLGA) and poly(D,L-lactic acid) (PDLLA). Both polymers are regulated by US FDA, which allows projecting future clinical use of fibers made from these materials. We manufactured three preforms and we subsequently drew optical fibers with a standard heat-draw tower. We describe the chemical properties of the materials throughout the whole production chain from polymer granulates to preforms and then to optical fibers. We look into to the influence of the processing on the molecular weight and thermal characteristics of the polymers. Our step-index bioPOF with an outer diameter of 1000 ± 50 μm and a core of around 570 ±30 μm features record low attenuation of 0.26 dB∕cm at 950 nm for step index bioPOF, and a numerical aperture of 0.163. Immersion in phosphate-buffered saline (PBS) leads to hydrolytic degradation of the bioPOFs over a period of 3 months, accompanied with a 91% molecular weight loss. From the degradation study results, we anticipate that our bioPOFs can be used for biophotonic applications requiring deep tissue light delivery, such as photodynamic therapy.
We demonstrate a biodegradable and biocompatible unclad optical fiber made from poly(D,L-lactic acid) (PDLLA), which is a well-known and commercially available amorphous polyester. We first deal with the chemical and optical characterization of the bulk polymer material and we report on the influence of the processing on the molecular weight and thermal properties of the polymer, during both the preform preparation and the fiber drawing process. We then proceed to the optical characterization based on spectral attenuation measurements using the cutback method and dispersion measurements. We also determine the thermo-optic coefficient. Finally, we confirm the in vitro degradation in phosphate buffered saline (PBS) of our PDLLA fibers. From the results and considering that PDLLA is an FDAregulated material, we anticipate that our optical fibers are valid candidates for medical applications involving in vivo light delivery, such as for example photodynamic therapy.
Nanostructured GRIN components are optical elements which can have arbitrary refractive index profile while retaining flat-parallel entry and exit facets. They are composed of more than 9000 individually placed glass subwavelength rods made of two types of glass with different refractive indices. They are developed using a standard stack-and-draw method used for fibre drawing. The refractive index profile of the nanostructured GRIN element can be described by the effective refractive index theory when the diameter of the individual rods are sufficiently smaller than the wavelength. In this paper we show that use of glasses designed for high diffusion and high temperatures during drawing process allows to develop parabolic nanostructured GRIN microlenses with rod diameter larger than wavelength. In particular, we have developed a GRIN microlens with diameter of 115 μm composed of 115 rods on diagonal. Our GRIN microlens has a length of 200 μm and a working distance equal to 1.05 mm, with focal spot of 8.5 μm measured for the 658 nm wavelength. We experimentally verified its imaging properties. Image resolution higher than 3.25 μm was measured.
We report for the first time successful inscription of high reflectivity Bragg grating in nanostructured core active fiber. Nanostructurization of the fiber core allows to separate the active and photosensitive areas and to distribute them all over the core. As a result unfavorable clustering between germanium and ytterbium particles is avoided. The distribution of discrete glass areas with feature size smaller than λ/5 results in effectively continuous refractive index profile of the fiber core. We present a single-mode fiber with built-in Bragg grating for laser application with the core composed of ytterbium and germanium doped silica rods. The core structure is arranged as a regular lattice of 1320 doped with ytterbium and 439 doped with germanium silica glass rods. The average germanium doping level within the core of only 1.1% mol allowed efficient inscription of Bragg grating. The nanostructured core was 8.6 μm and the internal cladding was 112 μm in diameter coated with low index polymer to achieve the double-clad structure. In the first proof-of-concept in the laser setup we achieved 35 % of slope efficiency in relation to launched power for the fiber length of 18 m. The output was single-mode with spectrum width below 1 nm. The maximum output power limited by pumping diode was 2.3 W. The nanostructurization opens new opportunities for development of fibers with a core composed of two or more types of glasses. It allows to control simultaneously the refractive index distribution, the active dopants distribution and photosensitivity distribution in the fiber core.
We study optical properties of gradient index vortex masks based on an effective medium approach. We consider masks with single charge developed using two types of nanorods made of thermally matched low and high refractive index glasses. Optical performance of generated vortices are analyzed in terms of glass refractive index difference and spatial dimension of the components. A fabricated vortex mask has been combined with single mode optical fiber. Optical performance of the resulting fiber integrated vortex mask is characterized and discussed.
We report a development of microscopic size gradient index vortex masks using modified stack-and-draw technique. Vortex mask has a form of tens of microns thick, flat-surface all-glass plate. Its functionality is determined by internal nanostructure composed of two types of soft glass nanorods. Their spatial arrangement ensures that the average refractive index mimics continuous refractive index distribution imposing azimuthal phase modulation of optical beam. The mask of thickness of 40 microns is used to demonstrate generation of optical vortices with charges 1 and 2, in the femtosecond and cw regimes, respectively.
We study optical properties of the gradient index vortices obtained using effective medium approach. Vorteces with charge +1 has been was developed using two types of nanorods made of thermally matched low and high refractive index glasses. Their optical properties of vortices are analyzed in the context of glass refractive index and size of the components. Consequently vortex has been integrated with single mode optical fiber and such a system is analyzed.
In this paper, we demonstrate the feasibility of using the nanostructured micro-optics technology to create a large
diameter quantized elliptical microlens. Nanostructured gradient index elements have discrete internal structure with
feature sizes much smaller than the wavelength of the incident light. The nanostructured lens is composed of two silicate
glasses with various refractive indexes. Large diameter elliptical microlens is developed. Optical performance of
microlens is verified numerically. Effective focal lengths of 220 and 116 for are predicted for wavelength of 1300 nm.
We present the design and fabrication details of a customised nanostuctured form birefringent material based upon a
second order effective medium theory composite composed of two mechanically and thermally matched soft
glasses. The design, which shows uniform birefringence over several hundred nanometres, is fabricated using a
modified stack-and-draw method to produce a final element with feature sizes in the 50-100nm range. A method for
measuring the effective birefringence of the composite material is presented along with the preliminary results from
the fabricated component.
In this paper we report on the fabrication, optical properties and imaging capabilities of nanostructured gradient index
microlenses with diffraction limited performance and good chromatic behaviour. We introduce a new fabrication concept
for the development of large diameter nanostructured gradient index microlenses based on quantised gradient index
profiles and the use of nanostructured meta-rods. We show the dependence of the quality of performance on the number
of refractive index levels and the overall lens diameter. The practical limit of the proposed method for fabricating
nanostructured GRIN microlenses is determined to be 120μm for 7 discrete levels of nanostructured meta-rod refractive
index. The fabricated microlenses show good achromatic behaviour - the observed working distances for illumination at
wavelengths of 633 nm and 850 nm are 43μm and 40μm, respectively, while the focal spot sizes remain the same for
We present a novel approach to the fabrication of diffractive optical elements. Unlike traditional diffractive optical
elements, the different phase shifts are obtained through a refractive index variation by using different types of glass.
This approach results in a completely flat element which is easy to integrate with other optical components. For
fabrication of the test DOE structures we have used the stack-and-draw technique. This method, which was originally
developed for the fabrication of photonic crystal fibres, has been modified to allow the fabrication of nanostructured
micro-optical components. In this paper we present the results from proof of concept periodic checkerboards fabricated
on a square and hexagonal lattice with feature sizes of 8μm and 46μm. The components were fabricated from two types
of rods made of the low refractive index silicate glass and the high refractive index of lead-silicate glass. The measured
characteristics of the fabricated components are presented The influence of fabrication-induced structure distortions on
the optical performance of the components is discussed.
In this paper we report the in-house synthesis of optical grade PMMA suitable for fiber development and fabrication of a
large core micro-structured polymer optical fiber (mPOF). We have designed an mPOF with a core area of 580 μm2 and
single mode performance at a wavelength of 650 nm. The photonic cladding is composed of 3 rings of air holes with a
filling factor of 0.58 ensuring in practice a single mode performance at the design wavelength of 650 nm. The designed
mPOF fiber was fabricated using the stack and draw technique, however some deformation of the structure of the
photonic cladding has been observed during final stage of fiber drawing. The influence of this development imperfection
on the overall fiber performance has been modeled. Finally the optical properties of the fabricated fiber were measured
and a comparison between these and the modeled properties was made.
In this paper results of soft glass single mode photonic crystal fibers (PCF) fabrication are presented. Using "stack and
draw" technique a few kinds of PCFs (various core sizes and filling factors) made of multicomponent glasses has been
successfully fabricated. Two glasses, developed in-house at the Institute of Electronic Materials Technology (ITME),
have been used. High refractive index (nD=1.94) lead-bismuth-gallate glass (PGB-08) and borosilicate glass (NC21A).
We have achieved attenuation 3.9 - 5.1dB/m (λ=806nm) for fibers made of NC21A glass and 15dB/m (λ=632.8nm) for
PBG08 glass. Glasses attenuation: NC21A - 3.2dB/m, PBG-08 - 14.5dB/m. Fibers have very regular photonic cladding
with filling factor in range 0.2 - 0.7.
In this paper we report on design and development of three types of the soft oxide glasses devoted to microstructured
optical fibers manufacturing. The lead-bismuth glasses are synthesized in three-component oxide system of PbO-Bi2O3-
Ga2O3 and in a complex five-component oxide system of SiO2-Ga2O3-Bi2O3-PbO-CdO. The tellurite glasses are
synthesized in oxide system of TeO2-WO3-PbO-Na2O-Nb2O5 with various concentration of WO3 (5-38%mol) and PbO
(0-18%mol). Measurements of glass transmittance are performed over the range 200nm-10μm. Linear thermal expansion
coefficients and characteristic temperatures of glasses are determined based on dilatometer and Leitz heat microscope
measurements. A use of Differential Scanning Calorimetry (DSC) method and crystallization tests (isothermal treatment)
allows estimating the thermal stability of the glasses and susceptibility to crystallization. As a reference, similar
measurements are performed for commercially available lead-silicate glasses SF57 and SF6, which are considered for
development of nonlinear microstructured fibres. The glasses with an optimum resistance for devitrification during
multiple thermal processing are selected among all developed glasses for further fibre development. We present a
method for development of preform and subpreform elements as tubes, capillaries and rods used in the stack-and-draw
technique of the fiber manufacture. We report also successful development of subpreform components of
microstructured fibers based on selected tellurite and lead-bismuth glasses.
In this work we designed and made a photonic crystal structure with a photonic band gap around 532 nm wavelength.
The structure was to be made from two commercially available glasses. Both should have similar temperature
coefficients (alpha), also melting and softening temperatures should be as close as possible in order to thermally process
both glasses together. In addition the refractive indexes of chosen glasses should be as different as possible in order to
facilitate a wide band gap. The pair of glasses that met those requirements is LLF1 and SF6 produced by Schott. For
those two glasses we performed a series of computer simulations using MIT MPB software. After checking various
structures the widest band gap for the 532 nm wavelength was found for the hexagonal structure of high dielectric
constant rods in low index material with a linear fill factor of 0.12 and a lattice constant 3.75 μm. This structure was
manufactured using the stack and draw method. The measurements of the final structure made by ESM show that it is
regular, with diffusion between glasses at the manageable level. This assures that manufacture process is repeatable.
In this paper we report on fabrication of all-Solid photonic Cladding and Air Core fiber (SCAC fiber). As far as we know it is a first reported fabrication of such PCF. Microrods are made of commercially available lead-oxide F2 glass (SCHOTT Inc.) with a refractive index nD=1.619, while as background we use a borosilicate NC21 glass synthesized in-house at ITME with a refractive index nD=1.533. A fabricated fiber has a lattice constant of Λ≈7.49μm and microrods diameter of d≈4.0μm. Air core has a diameter of DR=3.67μm and total fiber diameter is Dfiber=123.80μm.
In this paper we report on use stack and draw technique to develop volume 2D photonic crystals made of two types of
soft glasses with a large difference of refractive index. Existence of partial photonic bandgap in the material is predicted
Photonic crystals are wavelength-scale periodic structures built from dielectrics with different refractive indexes As
standard 2D photonic crystals are fabricated by lithographic methods, but in this case only planar structure can be
obtained. We have adapted stack and draw technique that is usually used for photonic crystal fiber fabrication to develop
volume 2D photonic crystals.
Technology allows fabrication of high contrast structures with air holes as well as low contrast solid-all structures where
air holes are replaced with glass micro rods of refractive index. Use of soft glasses with a high difference in refractive
index allows development of a structure where partial photonic band gap exists. The proposed method offers possibility
of fabrication volume 2D photonic crystal with a diameter in the order of 1 mm and height of a few mm. Large area
photonic crystals are very attractive as new optical material named 'photonic glass' with built-in photonic bandgap
functionality. Preliminary fabrication test were performed for two pairs of soft glasses NC21/F2 and SK222/Zr3. The
considered glasses are thermally matched and are synthesized in-house except of F2 glass (standard Schott glass).
Obtained structures are regular with some defects on the borders between intermediate performs. Some glass diffusion is
observed between Zr3 and SK222 glasses. With this technique a 2D photonic crystal with a hexagonal lattice was
fabricated with a pair of soft glasses SK222 and Zr3. Microrod diameter is 749nm and lattice constant 1110 nm.
Photonic crystal consists of 166421 elements (425 elements on diagonal) and its total surface is about field ~0,178mm2.