Optical spectroscopy in a shocked liquid

Duvall, G. E.; Ogilvie, K.; Wilson, R. B.; Bellamy, P. M.; Wei, P. S.

doi:10.1038/296846a0

Cited by 45 publications

(14 citation statements)

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“…Possible explanations include physical enhancement of etching due to amorphization, high defect concentration, [17] and shock-induced chemical modification. [5,4,18] Our current conjecture is that compaction of the amorphous part (region B in Fig. 1) causes a decrease of the average Al-O-Al angle, similar to that of the Si-O-Si angle in high-pressure silica.…”

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confidence: 78%

“…Such a pulse ionizes the focal volume almost instantaneously within one or few optical cycles by multiphoton absorption and launches a shock wave with subsequent fast (< 100 ns) thermal quenching. Transitions leading to different materials phases [2][3][4] with altered chemical properties [5,6] are expected to be formed.Here, we demonstrate control over the crystallinity and chemical reactivity of sapphire (Al 2 O 3 ) using femtosecondpulse exposure. Crystalline-to-amorphous and amorphous-topolycrystalline transitions were induced inside a sapphire sample using single-and multi-pulse irradiation, respectively.…”

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confidence: 99%

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Control over the Crystalline State of Sapphire

et al. 2006

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Phase transitions of solid-state materials can be controlled optically by electronic excitation. In semiconductors, the semiconductor-to-metal transition occurs upon excitation of approximately 10 % of the valence electrons.[1] This bandgap collapse occurs nonthermally, faster than the thermal-energy transfer from electrons to atoms when ultrashort pulses are utilized. In dielectrics, a metallic plasma state can be created at the focus of a typical tightly focused 100 nJ/200 fs pulse, creating a ∼ 10 14 W cm -2 intensity within a volume of subwavelength cross section. Such a pulse ionizes the focal volume almost instantaneously within one or few optical cycles by multiphoton absorption and launches a shock wave with subsequent fast (< 100 ns) thermal quenching. Transitions leading to different materials phases [2][3][4] with altered chemical properties [5,6] are expected to be formed.Here, we demonstrate control over the crystallinity and chemical reactivity of sapphire (Al 2 O 3 ) using femtosecondpulse exposure. Crystalline-to-amorphous and amorphous-topolycrystalline transitions were induced inside a sapphire sample using single-and multi-pulse irradiation, respectively. Wet etching of the amorphized sapphire in an aqueous solution of hydrofluoric acid showed extremely high selectivity (> 10 4 , calculated as the ratio of the channel's lengthening to its widening) relative to that of the crystalline and polycrystalline phases. This method allowed us to fabricate a 3D network of channels without apparent constraints on their length. The processing of sapphire, the most chemically inert and the hardest oxide, opens new opportunities in different industries; for example, sapphire substrates can be patterned for the growth of defect-free GaN in high-luminosity light-emitting diodes (LEDs) and laser diodes (LDs).The femtosecond pulses used in our experiments possess a peak power of tens of killowatts, which is much lower than the threshold for self-focusing (several megawatts), allowing the unique conditions of energy delivery to the focal volume to be exploited by keeping the nonlinear effects of light propagation negligible. The benchmark feature size for 3D nanostructures, usually set at 100 nm, can be surpassed by using tightly focused femtosecond pulses. [7] In crystalline dielectrics and glasses, the dielectric breakdown, a full ionization of the focal volume, causes extensive crack formation when pulses longer than 1 ps are utilized.[8] However, we show that in the case of femtosecond pulses, the photomodified region can be elastically sustained without crack formation inside the crystalline phase as long as it is confined within small sub-micrometer dimensions. Figure 1 shows a typical transmission electron microscopy (TEM) image of the cross section of the photomodified region made by a single femtosecond pulse inside sapphire. The di- COMMUNICATIONS

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Control over the Crystalline State of Sapphire

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“…The shockmodified materials can possess a different crystalline structure and form high-pressure phases with properties never used before for practical applications. [2][3][4][5][6][7] Control over phase transitions and, especially glass transition, becomes feasible due to very fast thermal quenching rates when sub-1 ps pulses are employed. Ultra-fast thermal quenching is expected to create new ceramics, glasses, and new composite nano-structured materials.…”

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confidence: 99%

Three-Dimensional Micro- and Nano-Structuring of Materials by Tightly Focused Laser Radiation

Juodkazis¹,

Mizeikis²,

Matsuo³

et al. 2008

Bulletin of the Chemical Society of Japan

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Three-dimensional laser microfabrication blends microscopy, optical nonlinear phenomena, photomodification, laser trapping, and creates novel possibilities for fabrication of micro-and nano-structures in a wide range of materials. This work reviews various implementations of laser photo-structuring and micromanipulation applied to photo-modification of various materials: glasses, crystals, polymers, gels, and liquid crystals.

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“…We demonstrate here that in such conditions nanovoids are formed by the extreme temperatures and pressures created by optical breakdown and these drive shock and rarefaction waves in the surrounding material. It is possible that new materials [10 -12] with altered chemical properties [13] could be formed by such micro-explosions.The interaction between an intense laser pulse and the material is fundamentally different when the laser beam is tightly focused inside a transparent solid rather than on its surface. Inside the solid the interaction zone containing high-energy density is confined inside cold and dense material.…”

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Laser-Induced Microexplosion Confined in the Bulk of a Sapphire Crystal: Evidence of Multimegabar Pressures

et al. 2006

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Extremely high pressures ( 10 TPa) and temperatures (5 10 5 K) have been produced using a single laser pulse (100 nJ, 800 nm, 200 fs) focused inside a sapphire crystal. The laser pulse creates an intensity over 10 14 W=cm 2 converting material within the absorbing volume of 0:2 m 3 into plasma in a few fs. A pressure of 10 TPa, far exceeding the strength of any material, is created generating strong shock and rarefaction waves. This results in the formation of a nanovoid surrounded by a shell of shock-affected material inside undamaged crystal. Analysis of the size of the void and the shock-affected zone versus the deposited energy shows that the experimental results can be understood on the basis of conservation laws and be modeled by plasma hydrodynamics. Matter subjected to record heating and cooling rates of 10 18 K=s can, thus, be studied in a well-controlled laboratory environment. DOI: 10.1103/PhysRevLett.96.166101 PACS numbers: 81.07.ÿb, 47.40.Nm, 62.50.+p, 81.40.ÿz The study of matter in conditions of extreme pressure and temperature is an exciting area of condensed matter physics relevant to the formation of new materials and modeling the state of matter inside stars and planets. Creation of such extreme conditions in the laboratory is, however, a formidable experimental task. So far, pressures in excess of 0.1 TPa have been obtained using a diamond anvil in stationary conditions, while transient pressures behind shock waves generated by chemical or nuclear explosions or generated using powerful lasers up to 50 TPa have been reported [1,2]. Here we present experimental evidence that one can create TPa pressures, many times the strength of any material, using low energy pulses from a conventional tabletop laser.Recent studies have demonstrated [3][4][5][6][7][8] that sub-ps laser pulses tightly focused inside transparent dielectrics (glasses, crystals, and polymers) can produce detectable sub-micrometer-sized structural modifications, including voids. This requires intensities in excess of 10 14 W=cm 2 which results in a highly nonlinear light-matter interaction with most dielectrics being ionized early in the laser pulse. To achieve such high intensities the laser beam should be tightly focused using high numerical aperture optics into a spot whose dimensions are of the order of the laser wavelength ( ).Previously the formation of voids in silica was associated with self-focusing of the laser beam [3]. In fact void formation can occur in conditions favorable for selffocusing if the beam is weakly focused into the sample [9]. Previously, however, there has been no systematic study of void formation by single fs pulses in conditions when self-focusing cannot occur. We demonstrate here that in such conditions nanovoids are formed by the extreme temperatures and pressures created by optical breakdown and these drive shock and rarefaction waves in the surrounding material. It is possible that new materials [10 -12] with altered chemical properties [13] could be formed by such micro-explosions.The inte...

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Optical spectroscopy in a shocked liquid

Cited by 45 publications

References 5 publications

Control over the Crystalline State of Sapphire

Control over the Crystalline State of Sapphire

Three-Dimensional Micro- and Nano-Structuring of Materials by Tightly Focused Laser Radiation

Laser-Induced Microexplosion Confined in the Bulk of a Sapphire Crystal: Evidence of Multimegabar Pressures

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