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.
Laser-Solid Interactions for Materials Processing, at 2000 Materials Research Science Meeting (San Francisco, CA), Wednesday, April 26, 2000:
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, a localized change in the index of refraction is produced, i.e. the material is damaged. By scanning the focus through the sample, very precise, three-dimensional... Read more about Laser-Solid Interactions for Materials Processing
Numerical aperture dependence of damage and white light generation from femtosecond laser pulses in bulk fused silica, at Photonics West 2002 (San Jose, CA), Thursday, January 24, 2002:
The femtosecond laser has become an important tool in the micromachining of transparent materials. In particular, focusing at high numerical aperture enables structuring the bulk of materials. At low numerical aperture and comparable energy, focused femtosecond pulses result in white light or continuum generation. It has proven difficult to damage transparent materials in the bulk at low NA. We have measured the threshold energy for continuum generation and for bulk damage in fused silica for numerical apertures between 0.01 and 0.65. The threshold for continuum generation exhibits a minimum... Read more about Numerical aperture dependence of damage and white light generation from femtosecond laser pulses in bulk fused silica
Manipulating matter with light, at Physics Colloquium, University of Missouri-Columbia (Columbia, MO), Thursday, February 26, 2004:
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 Manipulating matter with light
SC 541: An Introduction to Femtosecond Laser Techniques, at Photonics West 2006 (San Jose, CA), Sunday, January 22, 2006:
General Course Description: This interactively taught half-day course provides basic knowledge of the measurements of and research with femtosecond laser pulses. Beginning with the basic principles of the interaction of light and matter, we'll discuss the interaction of intense short pulses with matter. Using worksheets we'll address a number of common conceptual misconceptions in an interactive and collaborative setting.

Benefits Learning outcomes:

This course will enable you to

  • Explain the basis for the electronic and optical properties of...
Read more about SC 541: An Introduction to Femtosecond Laser Techniques
Femtosecond laser micromachining, at DEPS Ultrashort Pulse Laser Workshop (Newton, MA), Tuesday, June 30, 2009:
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.
Laser-induced microexplosions in transparent materials: microstructuring with nanojoules, at Photonics West 1999 (San Jose, CA), Tuesday, January 26, 1999
We tightly focus femtosecond laser pulses in the bulk of a transparent material. The high intensity at the focus causes nonlinear absorption of the laser energy, producing a microscopic plasma and damaging the material. The tight external focusing allows high intensity to be achieved with low energy, minimizing the effects of self-focusing. We report the thresholds for breakdown and critical self-focusing in fused silica using 110-fs pulses at both 400-nm and 800-nm wavelength. We find that permanent damage can be produced with only 10 nJ (25 nJ) for 400-nm (800-nm) pulses, and that the... Read more about Laser-induced microexplosions in transparent materials: microstructuring with nanojoules
Femtosecond laser micromachining of bulk glass at oscillator energies, at Gordon Conference on Nonlinear Optics, Colby Sawyer College (New London, NH), Tuesday, July 27, 1999:
Using femtosecond laser pulses generated by a 25-MHz Ti:Sapphire laser oscillator, we micromachine bulk glass. The laser is focused by a 1.4 numerical aperture microscope objective, allowing the breakdown threshold to be reached with modest energies (4.5 nJ). Single-shot damage is sub-micron in size. Because the pulses arrive faster than energy can diffuse out of the focal volume, multiple shot damage with this laser is thermal in nature. Successive pulses add more and more heat to the sample, melting a micron-sized volume. Using this thermal machining, we have written single-mode waveguides... Read more about Femtosecond laser micromachining of bulk glass at oscillator energies
Direct writing of optical waveguides in bulk glass using a femtosecond laser oscillator, at MRS Spring Meeting (San Francisco, CA), Tuesday, April 17, 2001:
In recent years, femtosecond lasers have proven to be extremely useful for micromachining the surface and bulk of transparent materials. When a femtosecond laser pulse is focused into a transparent material, the intensity in the focal volume can become high enough to cause absorption through nonlinear processes, leading to optical breakdown and permanent structural change to the material. Because the absorption is nonlinear, this structural change can be localized in the bulk of the sample, allowing a three-dimensional structure to be micromachined. In this paper, we show that by focusing a... Read more about Direct writing of optical waveguides in bulk glass using a femtosecond laser oscillator
Femtosecond Micromachining of Transparent Materials, at International School of Atomic and Molecular Spectroscopy (Erice, Sicily), Friday, May 23, 2003:
We present an overview of femtosecond microstructuring of transparent materials. Bulk structuring of transparent materials can be achieved by focusing high-intensity femtosecond pulses. The morphology of the structures depends on the incident energy per pulse and on the focusing conditions. At high focusing conditions the damage threshold in silicate glasses is just a few nanojoules. This energy range is available from an oscillator. We have demonstrated laser writing of embedded waveguides in silicate glasses with a femtosecond oscillator. Laser machining at high laser repetition rate... Read more about Femtosecond Micromachining of Transparent Materials
Optical waveguide fabrication for integrated photonic devices, at Optical and Electronic Device Technology for Access Network: Nanophotonics and functional device technology (San Jose, CA), Thursday, January 27, 2005:
The dynamic nature of future optical networks requires high levels of integration, fast response times, and adaptability of the optical components. Laser micromachining circumvents the limitations of planar integration, making three-dimensional integration possible and allowing dense packaging of optical devices with no alignment requirements. Femtosecond micromachining provides the analog of circuit printing by wiring light between various photonic devices as well as printing the actual photonic device into a single or various substrates. Oscillator-only machining has several advantages over... Read more about Optical waveguide fabrication for integrated photonic devices
SC 541: An Introduction to Femtosecond Laser Techniques, at Photonics West 2007 (San Jose, CA), Wednesday, January 24, 2007:
General Course Description: This interactively taught half-day course provides basic knowledge of the measurements of and research with femtosecond laser pulses. Beginning with the basic principles of the interaction of light and matter, we'll discuss the interaction of intense short pulses with matter. Using worksheets we'll address a number of common conceptual misconceptions in an interactive and collaborative setting.

Benefits Learning outcomes:

This course will enable you to

  • Explain the basis for the electronic and optical properties of...
Read more about SC 541: An Introduction to Femtosecond Laser Techniques
Femtosecond laser micromachining, at Extreme photonics Summer School: Ultrafast Lasers and Applications, University of Ottawa (Ottawa, ON, Canada), Thursday, June 26, 2014:
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.
Laser induced microexplosions in transparent materials, at CLEO/QELS '97 (Baltimore, MD), Friday, May 23, 1997
We recently discovered that 200-nm diameter structures can be created inside transparent materials by ultrafast-laser driven microexplosions. Applications include high-density 3-D data storage, fabrication of 3-D optical elements, and novel materials processing. We present the results of optical and structural examinations and discuss the physical processes involved.

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