Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

D. Seo, J. M. Gregory, Leonard C Feldman, N. H. Tolk, P. I. Cohen

Research output: Contribution to journalArticle

18 Citations (Scopus)

Abstract

We report wavelength- and intensity-dependent transmission measurements of intense mid-infrared radiation from the Vanderbilt free-electron laser in single-crystal Ge(100) in the wavelength range of 2.8-5.2 μm. This range accesses both the direct and indirect energy gaps in Ge, requiring in each case either two or three photons (2PA or 3PA) for absorption. Large changes in the multiphoton absorption rate are seen at the direct-to-indirect and 2PA-to-3PA transitions. Photon interactions are dominated by free-carrier absorption (FCA), primarily due to holes. The entire absorption process is modeled with the two- and three-photon absorption coefficients (β and γ) as fitting parameters. Using newly measured values of the low-intensity FCA cross sections, we find a best fit to the data at 2.8 μm that is in agreement with theory and previous measurements. We report a ratio of 175 for β across the direct-to-indirect transition, and a ratio of 5 across the same transition for γ. These ratios are independent of systematic variations in free-carrier cross sections and beam diameter.

Original languageEnglish
Article number195203
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume83
Issue number19
DOIs
Publication statusPublished - May 4 2011

Fingerprint

Germanium
multiphoton absorption
Infrared lasers
Free electron lasers
Laser radiation
free electron lasers
infrared lasers
germanium
Photons
laser beams
photons
Wavelength
infrared radiation
wavelengths
absorption cross sections
absorptivity
Energy gap
Single crystals
Infrared radiation
single crystals

ASJC Scopus subject areas

  • Condensed Matter Physics
  • Electronic, Optical and Magnetic Materials

Cite this

Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation. / Seo, D.; Gregory, J. M.; Feldman, Leonard C; Tolk, N. H.; Cohen, P. I.

In: Physical Review B - Condensed Matter and Materials Physics, Vol. 83, No. 19, 195203, 04.05.2011.

Research output: Contribution to journalArticle

@article{5720a56ab90a43379025afc4a7168ab4,
title = "Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation",
abstract = "We report wavelength- and intensity-dependent transmission measurements of intense mid-infrared radiation from the Vanderbilt free-electron laser in single-crystal Ge(100) in the wavelength range of 2.8-5.2 μm. This range accesses both the direct and indirect energy gaps in Ge, requiring in each case either two or three photons (2PA or 3PA) for absorption. Large changes in the multiphoton absorption rate are seen at the direct-to-indirect and 2PA-to-3PA transitions. Photon interactions are dominated by free-carrier absorption (FCA), primarily due to holes. The entire absorption process is modeled with the two- and three-photon absorption coefficients (β and γ) as fitting parameters. Using newly measured values of the low-intensity FCA cross sections, we find a best fit to the data at 2.8 μm that is in agreement with theory and previous measurements. We report a ratio of 175 for β across the direct-to-indirect transition, and a ratio of 5 across the same transition for γ. These ratios are independent of systematic variations in free-carrier cross sections and beam diameter.",
author = "D. Seo and Gregory, {J. M.} and Feldman, {Leonard C} and Tolk, {N. H.} and Cohen, {P. I.}",
year = "2011",
month = "5",
day = "4",
doi = "10.1103/PhysRevB.83.195203",
language = "English",
volume = "83",
journal = "Physical Review B-Condensed Matter",
issn = "1098-0121",
publisher = "American Physical Society",
number = "19",

}

TY - JOUR

T1 - Multiphoton absorption in germanium using pulsed infrared free-electron laser radiation

AU - Seo, D.

AU - Gregory, J. M.

AU - Feldman, Leonard C

AU - Tolk, N. H.

AU - Cohen, P. I.

PY - 2011/5/4

Y1 - 2011/5/4

N2 - We report wavelength- and intensity-dependent transmission measurements of intense mid-infrared radiation from the Vanderbilt free-electron laser in single-crystal Ge(100) in the wavelength range of 2.8-5.2 μm. This range accesses both the direct and indirect energy gaps in Ge, requiring in each case either two or three photons (2PA or 3PA) for absorption. Large changes in the multiphoton absorption rate are seen at the direct-to-indirect and 2PA-to-3PA transitions. Photon interactions are dominated by free-carrier absorption (FCA), primarily due to holes. The entire absorption process is modeled with the two- and three-photon absorption coefficients (β and γ) as fitting parameters. Using newly measured values of the low-intensity FCA cross sections, we find a best fit to the data at 2.8 μm that is in agreement with theory and previous measurements. We report a ratio of 175 for β across the direct-to-indirect transition, and a ratio of 5 across the same transition for γ. These ratios are independent of systematic variations in free-carrier cross sections and beam diameter.

AB - We report wavelength- and intensity-dependent transmission measurements of intense mid-infrared radiation from the Vanderbilt free-electron laser in single-crystal Ge(100) in the wavelength range of 2.8-5.2 μm. This range accesses both the direct and indirect energy gaps in Ge, requiring in each case either two or three photons (2PA or 3PA) for absorption. Large changes in the multiphoton absorption rate are seen at the direct-to-indirect and 2PA-to-3PA transitions. Photon interactions are dominated by free-carrier absorption (FCA), primarily due to holes. The entire absorption process is modeled with the two- and three-photon absorption coefficients (β and γ) as fitting parameters. Using newly measured values of the low-intensity FCA cross sections, we find a best fit to the data at 2.8 μm that is in agreement with theory and previous measurements. We report a ratio of 175 for β across the direct-to-indirect transition, and a ratio of 5 across the same transition for γ. These ratios are independent of systematic variations in free-carrier cross sections and beam diameter.

UR - http://www.scopus.com/inward/record.url?scp=79961109923&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79961109923&partnerID=8YFLogxK

U2 - 10.1103/PhysRevB.83.195203

DO - 10.1103/PhysRevB.83.195203

M3 - Article

VL - 83

JO - Physical Review B-Condensed Matter

JF - Physical Review B-Condensed Matter

SN - 1098-0121

IS - 19

M1 - 195203

ER -