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Femtosecond laser microfabrication

We study the interaction of intense, femtosecond laser pulses with bulk transparent materials and use this interaction for material modification. The intensity of a femtosecond laser pulse can be high enough to cause nonlinear interactions between a transparent medium and the laser field. The material can strongly absorb energy from the laser field, producing free electrons in the material. This absorption can lead to damage or refractive index changes in the irradiated sample. The nature of the interaction between the laser pulse and the material depends on how the laser pulse is focused. When a powerful femtosecond laser pulse is tightly focused into a transparent sample, nonlinear absorption occurs only in the very small focal volume. This localization allows us to create patterns in three-dimensions inside transparent samples such as glass. For example, we have observed structures as small as 200-nm in diameter, offering exciting possibilities for high-precision microstructuring of transparent solids and for minimally disruptive laser nanosurgery.
Micromachining of bulk glass with tightly-focused femtosecond laser pulses, at XI International Symposium Ultrafast Phenomena in Spectroscopy, Academia Sinica (Taipei, Taiwan), Tuesday, October 26, 1999:
talk_279.pdf
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... Read more about Micromachining of bulk glass with tightly-focused femtosecond laser pulses
Micromachining and laser processing with ultrashort laser pulses, at Second International Symposium on Laser Precision Microfabrication (LPM2001) (Singapore), Wednesday, May 16, 2001:
talk_359.pdf
When femtosecond laser pulses are focused tightly into a transparent material, the intensity in the focal volume can become high enough to cause nonlinear absorption of laser energy. The absorption, in turn, can lead to permanent structural or chemical changes. Such changes can be used for micromachining bulk transparent materials. Applications include data storage and the writing of waveguides and waveguide splitters in bulk glass, fabrication of micromechanical devices in polymers, and subcellular photodisruption inside single cells. In this talk we will review recent results obtained in... Read more about Micromachining and laser processing with ultrashort laser pulses
Femtosecond Laser Micromachining: Applications in Technology and Biology, at Analytical Chemistry Seminar, University of Wisconsin, Madison (Madison, WI), Thursday, September 11, 2003:
talk_491.pdf
When femtosecond laser pulses are focused tightly into a transparent material, the intensity in the focal volume can become high enough to cause nonlinear absorption of laser energy. The absorption, in turn, can lead to permanent structural or chemical changes. Such changes can be used for micromachining bulk transparent materials. Applications include data storage and the writing of waveguides and waveguide splitters in bulk glass, fabrication of micromechanical devices in polymers, and subcellular photodisruption inside living cells. In this talk I will review recent results obtained in the... Read more about Femtosecond Laser Micromachining: Applications in Technology and Biology
Femtosecond laser micromachining: Applications in Technology and Biology, at The 8th International Conference on Laser Ablation (Banff, Canada), Monday, September 12, 2005:
talk_1139.pdf
When femtosecond laser pulses are tightly focused into a transparent material, the intensity in the focal volume is high enough to cause absorption through nonlinear processes. The absorption of the laser energy excites a submicrometer-sized region of plasma inside the material, and the energy is subsequently transferred to the atoms in the form of heat and shock waves. This process permanently alters solids and ablates cellular structures in biological media [1]. Applications include high-density data storage in three dimensions, writing of waveguides and waveguide splitters in bulk glass,... Read more about Femtosecond laser micromachining: Applications in Technology and Biology
Femtosecond laser micromachining, at Research talk (with video link to UTSI), University of Tennessee (Knoxville, TN), Thursday, April 3, 2008:
talk_1382.pdf
When femtosecond laser pulses are focused tightly into a transparent material, the intensity in the focal volume can become high enough to cause nonlinear absorption of laser energy. The absorption, in turn, can lead to permanent structural or chemical changes. Such changes can be used for micromachining bulk transparent materials. Applications include data storage and the writing of waveguides and waveguide splitters in bulk glass, fabrication of micromechanical devices in polymers, and subcellular photodisruption inside single cells.
Ultrafast laser induced microexplosions: explosive dynamics and sub-micrometer structures, at Photonics West 1998 (San Jose, CA), Monday, January 26, 1998
Tightly focused femtosecond laser pulses can be nonlinearly absorbed inside transparent materials, creating a highly excited electron – ion plasma. These conditions exist only in a small volume at the laser focus. This tight confinement and extreme conditions lead to an explosive expansion — a microexplosion. In solid materials, a microexplosion can result in permanent structural changes. We find that the damage produced by femtosecond pulses in this way is surprisingly small, with only a 200-nm diameter. Material left at the center of the microexplosion is either amorphous and less dense or... Read more about Ultrafast laser induced microexplosions: explosive dynamics and sub-micrometer structures
Micromachining optical waveguides using a femtosecond laser oscillator, at Optical Society of America Annual Meeting (Providence, RI), Wednesday, October 25, 2000:
talk_358.pdf
By tightly focusing femtosecond laser pulses, we achieve optical breakdown in a transparent material using only nanojoules of laser energy. Localized structural changes are produced in the focal volume and used for bulk micromachining. Using this technique, we fabricate single-mode optical waveguides and other photonics devices inside bulk glass.
Morphology and optical properties of femtosecond irradiated glass with variable pulse repetition rates, at Glass & Optical Materials Division Fall 2004 Meeting (Cocoa Beach, FL), Tuesday, November 9, 2004:
talk_1074.pdf
We investigated the morphology of femtosecond irradiated borosilicate glass with respected to two variables: the number of shots and the laser repetition rate. For the laser repetition rate we have covered the range from 250 kHz to 25 MHz. We identify two distinct regimes of femtosecond processing in the kHz to MHz range. As the time interval between pulses is reduced, we observe a transition from a repetitive modification process (identical to what is frequently called multiple shot damage) to a cumulative thermal mechanism. In the repetitive regime, each pulse acts independently and the... Read more about Morphology and optical properties of femtosecond irradiated glass with variable pulse repetition rates
Complex microstructures fabricated via two-photon absorption polymerization, at Macro 2006 - 41st Inernational Symposium on Macromolecules (Rio de Janeiro, RG, Brazil), Sunday, July 16, 2006:
talk_1334.pdf
Using acrylic resin and Lucirin TPO-L as photoinitiator, we fabricated complex microstructures via the process of two photon absorption (2PA) polymerization. We measured the 2PA cross-section of Lucirin TPO-L, which is the parameter responsible for the nonlinear process, and the value found is among the ones reported in the literature for common photoinitiators. We also carried out quantum chemistry calculation in order to correlate the nonlinear optical properties of this photoinitiator to its molecular structure.
Direct writing of metallic structures for metamaterial applications, at Tri-Service Metamaterials Review (Virginia Beach, VA), Wednesday, May 26, 2010:
talk_1631.pdf
Ultrafast-laser micromachining allows for 3D fabrication of structures much smaller than the diffraction limited laser spot size in transparent media such as glass. Under a linear regime, the media does not absorb light at the operating wavelength of the laser. However, using ultrafast pulses, we can obtain material modification through non-linear absorption. The technique can also be used to induce chemical reactions. High intensity femtosecond laser pulses can induce the photoreduction of metal ions through non-linear absorption. We use solutions containing metal salts to grow metal... Read more about Direct writing of metallic structures for metamaterial applications
Hydrogenated amorphous silicon laser micromachining for photonic devices, at SPIE Photonics West 2013, Synthesis and Photonics of Nanoscale Materials X (San Francisco, CA), Tuesday, February 5, 2013
Abstract Development of integrated photonic devices is becoming increasingly important in technological applications. Hydrogenated amorphous silicon (a-Si:H) provides a promising platform. Variations in hydrogen content produce large changes in refractive index and band gap, on the order of 0.1-1. Previous research has demonstrated waveguide fabrication using photolithography and ion implantation techniques, which requires many steps and is limited to 2D patterns. We have developed a laser micromachining technique to locally reduce the hydrogen content of a-Si:H in the laser focus to... Read more about Hydrogenated amorphous silicon laser micromachining for photonic devices
Femtosecond Materials Processing II: Nontransparent materials, at Tsing Hua Univeristy (Beijing, China), Wednesday, December 17, 2014:
talk_2386.pdf
The intersection of materials research and ultrafast optical science is producing many valuable fundamental scientific results and applications, and the trend is expected to evolve as new and exciting discoveries are made. Femtosecond laser micromachining presents unique capabilities for three-dimensional, material-independent, sub-wavelength processing. At the same time the surface processing of materials permits the creation of novel materials that cannot (yet) be created under other conditions. In the first part of this talk we will discuss how when the ultashort laser pulses are focused... Read more about Femtosecond Materials Processing II: Nontransparent materials

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