The fiber grating fabrication based on use of the phase masks is the most stable and accurate manufacturing technology. This paper presents a brief overview of holographic methods of phase masks and fiber Bragg gratings (FBGs) writing and characterization with emphasis on the chirped gratings. We discuss the range of FBG parameters enabled by current technological methods, as well as the relation between the accuracy of FBG parameters and the performance of FBG-based dispersion compensators. While holographic phase mask and FBG writing principles have much in common, the phase mask and FBG production is a unified technology where the quality of the FBG is determined by numerous factors in the process of fabrication. As one of the significant factors, we study the effect of mirror non-flatness on the group delay ripple of chirped FBG. The quality of phase masks and FBGs is often important to characterize directly. In this paper we consider holographic side-diffraction methods of their characterization, which are very accurate and provide the information that is not simple to obtain from spectroscopic measurements.

An experimental study is presented which evaluates the effects of various important exposure parameters on the quality of fiber Bragg gratings. The parameters addressed include laser repetition rate, fluence and intensity, total exposure dose, numbers of shots, fiber-mask separation and beam scanning speed. In the case of excimer laser writing of gratings, it is seen that the balance between exposure fluence and total dose is crucial in how strong a grating can written and its writing time. It is also observed that the laser repetition rate does not affect the grating quality and that a fiber-mask separation of around 50 - 200 μm is desirable for optimum gratings. The changes in grating quality with argon ion beam scanning speed and exposure power are presented.

Materials processing using copper vapor lasers is discussed with particular reference to the manufacture of photonics components. The visible and UV wavelengths available from the copper laser can both be used for efficient micromachining of inherently hard materials, such as ceramic, diamond and metal, as well as in the fabrication of fiber Bragg gratings.

During the last decade the development of fiber Bragg gratings (FBG) was forced by the ever growing demand on data transmission capacity. Fiber Bragg gratings support as filters, amplifiers, and stabilizers the entire optical network philosophy avoiding optical to electrical signal conversion. Whereas in the early 1990s the most gratings were manufactured by researchers with continuous wave (cw) laser sources, the excimer laser became a common tool for high throughput writing of Bragg gratings in the mid 1990s. The excimer laser is nowadays still the most efficient UV laser source which leads to low cost of operations compared to other UV sources. This paper presents the possibilities and advantages of excimer lasers in regards to writing of fiber Bragg gratings.

Silica-on-Silicon is a well established technology for the fabrication of low insertion loss planar lightwave circuits. The Ge-doped waveguide core material, deposited with low temperature plasma enhanced chemical vapor deposition and not subjected to high temperature annealing, is highly UV light photosensitive, due to residual Ge/Si-OH groups in the material that, similarly to hydrogen loading, can contribute to the formation of those defect centers responsible for the photosensitivity. Gratings have been fabricated using a pulsed 193 nm ArF excimer laser and a phase mask. 25 mm long gratings, written on standard straight waveguides, show a record 47 dB extinction ratio and 0.2 nm rejection bandwidth for TE polarization, without hydrogen loading. Such narrow linewidth filters could find application in dense WDM systems. We designed and fabricated a compact Add/Drop multiplexer based on a high bandwidth, 2x2 multimode interference device, having a Bragg grating written in the multi-mode region. The characterization for the TE polarization prove the proposed Add/Drop principle, showing, in correspondence of the dropped channel, a 30dB dip at the transmitted output and a reflection peak at the drop output, this last having a larger bandwidth, and around 3dB excess loss respect to the transmitted channels.

Fabrication and characterization of tracks in calcium fluoride and crystalline quartz are described. These tracks were created using ultrashort near-infrared (NIR) laser pulses in a manner similar to that of writing waveguides in glasses. Unlike the tracks in glasses the laser-written tracks in crystals have the depression of the refractive index. The magnitude of the depression is about 0.01 or more that may enable creation of high-contrast structures in crystals. Depending on the writing conditions the tracks' diameter may vary from around 1 micrometer to 10 micrometers.

We present the fabrication of three-dimensional waveguide structures indide fused silica using the femtosecond laser direct-writing technique. The guiding properties of a produced 1x3 splitter are studied in detail. By appropriate choice of the processing parameters a multimode entrance port can be generated which allows to vary the splitting ratio by changing the input coupling. The processing requirements for such splitter devices will be discussed.

We report on single mode active waveguides at 1.5 μm in Er:Yb-doped glass substrates fabricated with femtosecond laser pulses. A new spatial beam shaping approach for fabrication of waveguides with circular transverse profile is discussed, which uses an astigmatic beam and controls both beam waist and focal position in tangential and sagittal planes. The experimental results are well described by a simple nonlinear absorption model. The waveguides realized with this technique provide a significant enhancement in the whole Er-band, becoming interesting candidates for the realization of many photonic devices.

Investigations on two-photon polymerization of inorganic-organic hybrid materials initiated by femtosecond Ti:sapphire laser pulses are performed. The applied resins are designed for ultraviolet photo-lithography and contain photo-initiators sensitive to 390 nm radiation. These resins exhibit exceptionally good mechanical, optical, and chemical properties and can be microstructured by laser-enforced transition from liquid to solid state. These materials are transparent in the infrared, therefore, by tightly focusing femtosecond laser pulses into the volume of a liquid resin, two-photon polymerization can be initiated in a small focal region inside the liquid. First applications of this technique for the fabrication of three-dimensional microstructures and photonic crystals in inorganic-organic hybrid polymers with a structure size down to 200 nm and a periodicity of 450 nm are discussed.

Vacuum UV laser micromachining is used to produce microstructures in common photonics materials. The ablation etch rates of lithium niobate, fused silica and indium phosphide are measured at 157nm and angled facets and v-grooves are machined into the materials using a high NA mask projection system. The applicability of such micromachined structures for photonics devices is discussed and future developments outlined.

We report studies of material processing using the VUV F₂ laser which, by virtue of its low threshold, high resolution 'machining' capability, may bring advantage to laser-based optoelectronic and photonic device fabrication. For example, probe beam deflection and etch rate studies of polymethylmethacrylate (PMMA) show this has a low ablation threshold, F_T=20mJcm^-2, and a large effective absorption coefficient, 1.6 x 10⁵ cm^-1, at 157nm, permitting high-resolution etching at modest fluence. The smooth ablated surfaces and low degree of thermal damage obtained with this laser make it well suited to machining structures such as relief gratings in PMMA. We also describe new results on producing fiber Bragg gratings with the 157nm laser. It is shown that these gratings can be written in a non-sensitized single mode fiber (Corning HI 980) with a low fluence and low total dose.

Submicron surface-relief gratings were fabricated on fused silica by laser ablation with nanosecond (ns) pulses from a high-resolution F₂-laser processing station. The grating relief was generated by imaging a transmission amplitude grating with a Schwarzschild objective of 25x demagnification. The chrome-coated CaF₂ mask had been structured by laser ablation at 193 nm to form a line and space pattern of 20-μm period. The F₂-laser generated gratings on fused silica were characterized by SEM, AFM and diffraction of a HeNe laser beam, yielding a grating period of 830 nm and a corrugation depth of 250 nm. Surface-relief gratings on optical materials are required for various applications such as grating demultiplexers for telecommunication components, light couplers for planar optical waveguides, Bragg reflectors, or alignment grooves for liquid crystals. Laser ablation is a rapid and flexible method to generate custom grating designs on a variety of materials.

An easy and effective technique for locally oxidize, melt or remove Porous Silicon layers is presented and discussed. The method takes advantage from the very low thermal conductivity of Porous Silicon. With the aid of a focused laser beam, it is possible to reach temperatures of several hundreds °C at the illuminated spot. Results on fabrication of all-porous planar waveguides are presented and discussed. Preliminary results on the application of this technique for fabricating 2D and 3D photonic crystals are reported.

Laser ablation and laser smoothing of silica is investigated as a method of manufacturing custom micro-optics for use with high-power, diode laser arrays. A highly flexible machining regime has been identified that uses 30 to 60 microseconds square pulses, generated from a stabilized CO₂ laser by an acousto-optical modulator (AOM). Refractive optical surfaces with apertures of 1 mm x 1 mm have been generated by the multi-pulse, raster scanning method with cut depths in the range of 10 to 30 μm controlled to an accuracy of better than 150 nm. A subsequent laser "fire polishing" step to smooth out the surface, using the same laser system as for machining, but in a long pulse mode at an energy fluence that just avoids further ablation of the surface. The objective of the research is to produce rapid prototyping of arrays of refractive elements, to avoid the tooling or mask-writing steps of alternative methods. A particular interest is in the generation of corrective optical elements to improve the beam quality of arrays of diode laser bars.

A novel method for bonding micro optical components using a new joining process of silicon with glass is described. The process is based on selective heating with laser radiation forming a chemical bond at the interface of both joining partners. In order to characterize the locally selective bonding with laser (SLB) process, variations of laser parameters have been correlated with temperature measurements during bonding and the achieved bonding results. It was found that the temperature load outside the laser irradiated zone only lasted for seconds and remained below 300°C, so minimizing the heat load of the entire component. The result of the investigations was a parameter field producing reproducible and strong silicon glass bonds. Basic knowledge for the thermal process of bonding and an understanding of the recognized bond defects was developed. Finally advantages and disadvantages of SBL with silicon and glass are discussed with respect to micro assembly of optical parts for telecommunication components.

Plastic optical fibers (POF) continuously gained its importance during the last decade, since they are widely used in automotive applications for optical data communications (for e.g. MOST). The application of POF for in-flight-entertainment (IFE) optical networks in civil aircraft cabin areas is currently under investigation. Since it is expected that the optical networks will develop from a point-to-point network architecture to more complicated structures there will be a need for optical couplers distributing the signals to different suppliers. Typical applications would be for e.g. the distribution of optical data to IFE implemented within single seats of a seat row of an airplane. Within this work the fabrication of an optical 1x2 POF coupler by the Laser-LIGA technique is demonstrated. The Laser-LIGA technique compared to standard X-ray lithography is simpler and more cost effective. Moreover, the Laser ablation technique also allows rapid prototyping of the same structures. The POF couplers fabricated by this technology show insertion loss values down to about 5.6 dB, depending on the waveguide core material and exhibit good uniformity values in the order of 0.1 dB.

Excimer laser ablation is a microfabrication technique suitable for surface structuring of polymers because of their high UV absorption an often non-thermal ablation behavior. Due to its non-contact and direct-write nature, laser ablation has the potential to allow insertion of micro-optical functionality by surface structuring in a late phase of a heterogeneous assembly. This in contrary to many of its competitors in the microfabrication technology. In this paper we investigate how the technique can be applied to fabricate microlenses in polymer materials and report on the present status of experimental results. Based on scanning a polymer surface with a pulsed excimer beam along well-chosen multiple concentric contours, microlenses of arbitrary shape can be realized. Optical performance and lens surface quality are evaluated by imaging experiments, scanning electron microscopy and profilometer measurements. One particular application of microlenses deals with enhancing the optical power transfer efficiency in coupling from, to or between single mode optical fibers. By attaching a dedicated thin polymer layer on a fiber end, one is able to put a microlens on the fiber facet using excimer laser ablation. Current status of the experimental results will be discussed.

Focused laser micromachining in an optical microscope system is used to prototype packages for optoelectronic devices and to investigate new materials with potential applications in packaging. Micromachined thin fims are proposed as mechanical components to locate fibers and other optical and electrical components on opto-assemblies. This paper reports prototype structures which are micromachined in silicon carbide to produce beams 5 μm thick by (1) laser cutting a track in a SiC coated Si wafer, (2) undercutting by anisotropic silicon etching using KOH in water, and (3) trimming if necessary with the laser system. This approach has the advantage of fast turn around and proof of concept. Mechanical test data are obtained from the prototype SiC beam package structures by testing with a stylus profilometer. The Youngs modulus obtained for chemical vapor deposited silicon carbide is 360 +/- 50 GPa indicating that it is a promising material for packaging applications.

Laser radiation is used both for the deposition of dielectric Er:BaTiO₃ thin films and for material removal to generate wave guiding structures for photonic applications. Pulsed laser deposition with KrF excimer laser radiation (wavelength 248 nm, pulsed duration 20 ns) is used to grow dense, transparent amorphous or crystalline erbium doped BaTiO₃ thin films. Visible emission due to up-conversion luminescence (wavelength 528 nm and 548 nm) under excitation with diode laser radiation at a wavelength of 975 nm is investigated as a function of the erbium concentration and structural film properties. The dielectric films are micro machined to form optical wave guiding structures using Nd:YAG laser radiation (wavelength 532 nm, pulsed duration 40 ps) and Ti:sapphire laser radiation (wavelength 810 nm, pulse duration 63 - 150 fs) by scanning the focused laser beam relatively to the sample.