Femtosecond laser microfabrication

G. W. t Hooft, E. Mazur, J. M. Bienfait, L. J. F. Hermans, H. F. P. Knaap, and J. J. M. Beenakker. 1979. “The influence of a magnetic field on the thermal diffusion of polyatomic gas-noble gas mixtures.” Physica, 98A, Pp. 41–86. Publisher's VersionAbstract
Experiments on the influence of a magnetic field on the thermal diffusion (Dt) have been performed. Both the transverse coefficient, (D-tr/T), as well as the difference between the longitudinal coefficients, (D-// T), were measured for binary mixtures of N2, nD2, HD and nH2 with the noble gases Ar, Ne and He and for the system pH2-Ar. For most of these systems, the results can be adequately described with the dominant angular momentum polarization of the form WJJ. For some mixtures, however, a significant contribution from a second polarization (viz. WJ) was found to be present. The results are expressed in terms of effective molecular cross sections. Using these results and those earlier obtained for the magnetic field effect on the thermal conductivity, an estimate is made about the magnitude of the Senftleben-Beenakker effect on the diffusion.
C. B. Schaffer, A. O. Jamison, and E. Mazur. 2004. “Morphology of femtosecond laser-induced structural changes in bulk transparent materials.” Appl. Phys. Lett., 84, Pp. 1441–1443. Publisher's VersionAbstract
Using optical and electron microscopy, we analyze the energy and focusing angle dependence of structural changes induced in bulk glass by tightly-focused femtosecond laser pulses. We observe a transition from small density variations in the material to void formation with increasing laser energy. At energies close to the threshold for producing a structural change, the shape of the structurally changed region is determined by the focal volume of the objective used to focus the femtosecond pulse, while at higher energies the structural change takes on a conical shape. From these morphological observations, we infer the role of various mechanisms for structural change.
D. B. Wolfe, J. B. Ashcom, J. C. Hwang, C. B. Schaffer, E. Mazur, and G. M. Whitesides. 2003. “Customization of poly(dimethylsiloxane) stamps by micromachining using a femtosecond-pulsed laser.” Adv. Mater., 15, Pp. 62–65. Publisher's VersionAbstract
A femtosecond-pulsed Ti:sapphire laser is used to generate surface features in slabs of poly(dimethylsiloxane) with minimum dimensions of 1 mum-smaller than those available by rapid-prototyping techniques using transparency masks. The fabrication of magnetic field concentrators and the addition of custom features to a generic microfluidic channel (see Figure) demonstrate the utility of the technique.
D. S. Correa, P. Tayalia, G. Cosendey, D. S. Dos Santos, R. F. Aroca, E. Mazur, and C. R. Mendonca. 2009. “Two-Photon Polymerization for Fabricating Structures Containing the Biopolymer Chitosan.” Journal of Nanoscience and Nanotechnology, 9, Pp. 5845–5849. Publisher's VersionAbstract
Two-photon polymerization is a powerful tool for fabricating three-dimensional micro/nano structures for applications ranging from nanophotonics to biology. To tailor such structure for specific purposes it is often important to dope them. In this paper we report on the fabrication of structures, with nanometric surface features (resolution of approximately 700 nm), using two-photon polymerization of an acrylic resin doped with the biocompatible polymer chitosan using a guest-host scheme. The fluorescence background in the Raman spectrum indicates the presence of chitosan throughout the structure. Mechanical characterization reveals that chitosan does not affect the mechanical properties of the host acrylic resin and, consequently, the structures exhibit excellent integrity. The approach presented in this work can be used in the fabrication of micro- and nanostructures containing biopolymers for biomedical applications.
C. R. Mendonca, P. Tayalia, T. Baldacchini, and E. Mazur. 2006. “Three-dimensional microfabrication for photonics and biomedical applications.” In . Macro 2006 - 41st International Symposium on Macromolecules Proceedings. Publisher's VersionAbstract
We use two-photon absorption polymerization to fabricate microstructures containing compounds with interesting properties for optical and biomedical applications. Our investigations open the door to new applications in data storage, waveguides manufacturing, organic LEDs, optical circuitry and scaffold for bio-applications.
P. Tayalia, E. Mazur, and D. J. Mooney. 2011. “Controlled architectural and chemotactic studies of 3D cell migration.” Biomaterials, 32, Pp. 2634–2641. Publisher's VersionAbstract
Chemotaxis plays a critical role in tissue development and wound repair, and is widely studied using ex vivo model systems in applications such as immunotherapy. However, typical chemotactic models employ 2D systems that are less physiologically relevant or use end-point assays, that reveal little about the stepwise dynamics of the migration process. To overcome these limitations, we developed a new model system using microfabrication techniques, sustained drug delivery approaches, and theoretical modeling of chemotactic agent diffusion. This model system allows us to study the effects of 3D architecture and chemotactic agent gradient on immune cell migration in real time. We find that dendritic cell migration is characterized by a strong interplay between matrix architecture and chemotactic gradients, and migration is also influenced dramatically by the cell activation state. Our results indicate that Lipopolysaccharide-activated dendritic cells studied in a traditional transwell system actually exhibit anomalous migration behavior. Such a 3D ex vivo system lends itself for analyzing cell migratory behavior in response to single or multiple competitive cues and could prove useful in vaccine development.
J. B. Ashcom and E. Mazur. 2001. “Femtosecond laser-induced microexplosions in transparent materials.” In . LEOS 2001. Publisher's VersionAbstract
By focusing femtosecond laser pulses with high numerical-aperture microscope objectives, we micromachine optical glass using energies that are in the range of modern laser oscillators. When a femtosecond laser pulse is tightly focused inside a transparent material, energy deposition occurs only at the focus, where the laser intensity is high enough to cause absorption through nonlinear processes. When enough energy is deposited, the material is damaged and a localized change in the index of refraction is produced. By scanning the focus through the sample, very precise, three-dimensional microstructuring can be achieved.
M. Kamata, M. Obara, R. R. Gattass, L. R. Cerami, and E. Mazur. 2005. “Optical vibration sensor fabricated by femtosecond laser micromachining.” Appl. Phys. Lett., 87, Pp. 051106-1–051106-3. Publisher's VersionAbstract
We fabricated an optical vibration sensor using a high-repetition rate femtosecond laser oscillator. The sensor consists of a single straight waveguide written across a series of three pieces of glass. The central piece is mounted on a suspended beam to make it sensitive to mechanical vibration, acceleration, or external forces. Displacement of the central piece is detected by measuring the change in optical transmission through the waveguide. The resulting sensor is small, simple, and requires no alignment. The sensor has a linear response over the frequency range 20 Hz 2 kHz, can detect accelerations as small as 0.01 m/s2, and is nearly temperature independent.
C. B. Schaffer, T. N. Kim, J. F. Garcia, E. Mazur, A. Groisman, and D. Kleinfeld. 2004. “Micromachining of bulk transparent materials using nanojoule femtosecond laser pulses.” In . Boulder Damage Symposium. Publisher's VersionAbstract
Femtosecond lasers are very effective tools for three-dimensional micromachining of transparent materials. Nonlinear absorption of tightly focused femtosecond laser pulses allows energy to be deposited in a micrometer-sized volume in the bulk of the sample. If enough energy is deposited, localized changes in the material are produced (a change in refractive index, for example). These localized changes are the building blocks from which three-dimensional structures can be produced. With sufficiently tight focusing, the threshold for producing these changes can be achieved with pulse energies that are available directly from laser oscillators, offering greatly increased machining speeds and simpler, cheaper technology compared to using amplified lasers. In addition, the inter-pulse spacing from a laser oscillator is much shorter than the time required for energy deposited by one pulse to diffuse out of the focal volume. As a result, irradiation with multiple pluses on one spot in the sample leads to an accumulation of heat around the focal region. This localized heating provides another mechanism by which material properties can be altered. We demonstrate the three- dimensional fabrication of optical waveguides and microfluidic channels using pulse energies of only a few nanojoules to tens of nanojoules.
R. R. Gattass and E. Mazur. 2004. “Wiring light with femtosecond laser pulses.” In Photonics Spectra, 12: Pp. 56–60. Publisher's VersionAbstract
Shortly after the invention of the laser, researchers discovered that intense laser pulses can cause dielectric breakdown and structural change in materials. This breakdown was generally considered a tremendous nuisance, hindering both research and the development of more powerful lasers. Several decades later, however, laser-induced dielectric breakdown inside materials is wiedely used to create internal structural change. It is in this arena that lasers really stand out, as they afford the opportunity that no mechanical tool can: the processing of the bulk of a material without affecting its surface. Recent advances in this area of research make it possible to wire light from one point to another inside a transparent material, opening the door to the manufacturing of entirely monolithic, integrated optical circuitry.
C. R. Mendonca, S. Orlando, G. Cosendey, M. T. Winkler, and E. Mazur. 2007. “Femtosecond laser micromaching in the conjugated polymer MEH- PPV.” Applied Surface Science, 254, Pp. 1135–1139. Publisher's VersionAbstract
Femtosecond-laser micromachining of poly[2-methoxy-5-(2'1/2- ethylhexyloxy)- p-phenylene vinylene] (MEH-PPV) films is investigated using 130-fs pulses at 800-nm from a laser oscillator operating at 76-MHz repetition rate. We investigate the effect of pulse energy and translation speed on the depth and morphology of the micromachined regions. We quantified the MEH- PPV photobleaching induced by the fs-laser, and the conditions in which the emission of MEH-PPV is preserved after the micromaching.
K. Vora, S. Kang, S. Shukla, and E. Mazur. 2012. “Fabrication of disconnected three-dimensional silver nanostructures in a polymer matrix.” Appl. Phys. Lett., 100, Pp. 063120–063120-3. Publisher's VersionAbstract
We present a simple, one-step technique for direct-writing of a structured nanocomposite material with disconnected silver nanostructures in a polymer matrix. A nonlinear optical interaction between femtosecond laser pulses and a composite material creates silver structures that are embedded inside a polymer with submicrometer resolution (300 nm). We create complex patterns of silver nanostructures in three dimensions. The key to the process is the chemical composition of the sample that provides both a support matrix and controlled growth. The technique presented in this letter may offer a cost-effective approach for the fabrication of bulk optical devices with engineered dispersion. Copyright (2012) American Institute of Physics. This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
J. B. Ashcom, R. R. Gattass, E. Mazur, and Y. Chay. 2002. “Laser induced microexplosions and applications in laser micromachining.” In . 13th International Meeting on Ultrafast Phenomena. Technical Digest. Publisher's VersionAbstract
After reviewing some of the fundamentals of surface and bulk damage in transparent materials, we will present an overview of work being done in out laboratory on tighly focusing femtosecond pulses into the bulk of transparent materials with an emphasis on materials processing and micromachining.
E. Mazur and D. S. Chung. 1987. “Light-scattering from the liquid-vapor interface.” Physica, 147A, Pp. 387–406. Publisher's VersionAbstract
This paper presents light scattering spectra from the liquid-vapor interface of water and ethanol. Both quasi-elastic (Rayleigh) scattering and inelastic (Brillouin) scattering from fluctuations at the interface are observed. The spectra were obtained using a novel Fourier transform heterodyne technique that allows one to resolve the full Rayleigh-Brillouin triplet. Capillary waves travelling in opposite directions can therefore be separated, making the present technique suitable for studying nonequilibrium effects in interfaces.
T. Shih, R. R. Gattass, C. R. Mendonca, and E. Mazur. 2007. “Faraday rotation in femtosecond laser micromachined waveguides.” Opt Express, 15, Pp. 5809–5814. Publisher's VersionAbstract
We demonstrate magneto-optic switching in femtosecond-laser micromachined waveguides written inside bulk terbium-doped Faraday glass. By measuring the polarization phase shift of the light as a function of the applied magnetic field, we find that there is a slight reduction in the effective Verdet constant of the waveguide compared to that of bulk Faraday glass. Electron Paramagnetic Resonance (EPR) measurements confirm that the micromachining leaves the concentration of the terbium ions that are responsible for the Faraday effect virtually unchanged.