Femtosecond laser microfabrication

Fabrication of Structured Nanocomposite Materials for Three-Dimensional Metamaterial Applications We present a technique that combines top-down and bottom-up nanofabrication approaches to create a structured nanocomposite material. The structured nanocomposite material consists of three-dimensional (3D) silver nanostructures embedded inside a doped polymer matrix. The positioning of silver structures within the matrix is controlled via femtosecond laser irradiation. The key is to use a material combination that yields a stable background dielectric matrix while allowing nanostructure growth... Read more about Fabrication of Structured Nanocomposite Materials for Three-Dimensional Metamaterial Applications

Integrated diffractive optics has many applications in beam shaping and control on the micro-scale. Fabrication using lithography is limited to planar or layered geometries. We demonstrate fabrication of diffractive elements via direct laser writing. We have tested 3D diffraction gratings and zone plates designed for operation at visible wavelengths. Direct laser writing is a promising technique to fabricate integrated 3D and multi-layer diffraction optics. We have previously developed a laser writing technique that enables fabrication of disconnected metal structures in a polymer matrix,... Read more about Direct Laser Writing of 3-D Diffraction Gratings and Diffraction Optics

We produce sub-micron sized permanent damage in the bulk of dielectric materials using 110-fs laser pulses with only 40 nJ of energy. Tight external focusing (0.65 NA) of the ultrashort laser pulses enables us to achieve a high intensity at the focus with low laser energy. The high intensity leads to nonlinear absorption of the laser pulse by the material, resulting in permanent damage. Achieving high intensity with low energy reduces the effects of self-focusing, and eliminates the need for an amplified laser system. We report thresholds for damage and critical self-focusing in fused silica... Read more about Microstructuring of bulk transparent solids using nanojoule, femtosecond laser pulses

Light travels undisturbed through a window pane because glass is transparent -- light and glass don't interact. With a powerful femtosecond laser pulse, however, nonlinear processes give rise to light-matter interactions that open the door to new studies in materials science, chemistry, condensed matter physics, and life sciences. Even at very modest energies, the intensity of a tightly-focused, femtosecond laser pulse can be high enough to cause nonlinear absorption of laser energy by a transparent material. The absorption is confined at the focus producing extreme conditions in the... Read more about Microexplosions: controlling matter with light

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

We measured the two-photon absorption cross-section of Lucirin TPO-L and fabricated complex microstructures using it in acrylate resin. Using quantum chemistry calculations, we relate the nonlinear optical properties of the photoinitiator to its molecular structure.

An overview of research opportunities for undergraduate students at Harvard University in the summer of 2010.

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

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

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

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

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

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.