Clark School Home UMD
ECE

Events Calendar

Event Information

Ph.D. Dissertation Defense: Sina Zahedpour Anaraki
Tuesday, August 1, 2017
3:30 p.m.
IREAP Large Conference Room (ERF 1207)
For More Information:
Maria Hoo
301 405 3681
mch@umd.edu

ANNOUNCEMENT: Ph.D. Dissertation Defense

Name: Sina Zahedpour Anaraki

Committee members:
Professor Howard Milchberg, Chair
Professor Christopher Davis
Professor Julius Goldhar
Doctor Jared Wahlstrand
Professor Ki-Yong Kim, Dean's Representative

Date/Time: Tuesday, August 1, 2017 at 3:30pm

Place: IREAP Large Conference Room (ERF 1207)

Title: ULTRAFAST NONLINEAR RESPONSE OF ATOMIC AND MOLECULAR GASES IN NEAR-IR AND MID-IR REGIONS

Abstract:

There is a dynamical interaction between an ultrashort laser pulse and the medium it propagates through. At the shortest timescales, the near-instantaneous electronic response of the medium contributes to an induced polarization nonlinearity. On a longer timescale, the vibrational response can contribute, followed on even longer timescales by the rotational response. One of the major consequences of these nonlinearities is that they can induce the collapse and filamentation of the laser pulse, leading to ionization and plasma generation.

In this dissertation, measurements and theory are presented for both the fundamental atomic and molecular nonlinearities themselves (electronic, rovibrational, and ionization rates) in the range l=400nm-2600nm, and their applications. The media investigated are air constituents (Ar, N2, O2), H2, D2, and common transparent optical materials. In particular, in one application it is shown that in molecular gases like N2 and O2, the propagating laser electric field can pump a rotational wavepacket, producing molecular ensembles with both transient and long-lived (“permanent”) alignment components. This alignment, which generates quantum echoes (rotational revivals), can interact with the pulse that generated it (rotational nonlinearity) and with any pulses that may follow. We show that a properly timed train of ultrashort laser pulses can resonate with the rotational revivals, causing a “permanent” alignment in the gas which thermalizes and then drives a strong hydrodynamic response which can exceed that from the plasma heating by a filament.

 
 
 

This Event is For: Graduate • Faculty

Browse Events By Calendar

Calendar Home

« Previous Month    Next Month »

October 2017
SU M TU W TH F SA
1 2 3 4 5 6 7 w
8 9 10 11 12 13 14 w
15 16 17 18 19 20 21 w
22 23 24 25 26 27 28 w
29 30 31 w
Search Events

Events

Events Calendar
Submit Event

News

Newsroom
News Search
News Archives