


2019-01-18
ION HANCU
ION HANCU

2019-01-29
MARIA MAFFEI
MARIA MAFFEI

2019-02-13
BORIS BOURDONCLE
BORIS BOURDONCLE

2019-02-15
JORDI MORALES DALMAU
JORDI MORALES DALMAU

2019-02-22
FRANCESCO RICCI
FRANCESCO RICCI

2019-03-06
CLARA GREGORI
CLARA GREGORI

2019-03-26
ALEXIA SALAVRAKOS
ALEXIA SALAVRAKOS

2019-04-12
SENAIDA HERNANDEZ SANTANA
SENAIDA HERNANDEZ SANTANA

2019-04-15
DAVID RAVENTÓS RIBERA
DAVID RAVENTÓS RIBERA

2019-04-16
PETER SCHMIDT
PETER SCHMIDT

2019-04-29
CALLUM O’DONNELL
CALLUM O’DONNELL

2019-05-02
LUCIANA VIDAS
LUCIANA VIDAS

2019-05-03
HANYU YE
HANYU YE

2019-05-10
TANJA DRAGOJEVIC
TANJA DRAGOJEVIC

2019-05-17
FLAVIO BACCARI
FLAVIO BACCARI

2019-06-04
MARTINA GIOVANNELLA
MARTINA GIOVANNELLA

2019-07-02
OZLEM YAVAS
OZLEM YAVAS

2019-07-03
ALESSANDRO SERI
ALESSANDRO SERI

2019-07-11
RENWEN YU
RENWEN YU

2019-09-06
ALEXANDER BLOCK
ALEXANDER BLOCK

2019-10-04
MARCO PAGLIAZZI
MARCO PAGLIAZZI

2019-10-07
RINU MANIYARA
RINU MANIYARA

2019-10-15
ALEJANDRO POZAS-KERSTJENS
ALEJANDRO POZAS-KERSTJENS
Novel Pulsed Optical Parametric Sources in the Mid-Infrared and the Application Towards High-Resolution Molecular Spectroscopy


HANYU YE
May 3rd, 2019
HANYU YE
Optical Parametric Oscillators
ICFO-The Institute of Photonic Sciences
The mid-infrared (mid-IR) spectral region coincides with fundamental rotational-vibrational transitions of a large number of molecules in the gas phase. The strong interaction between mid-IR light sources and these gaseous molecules has enabled experimental investigations of energy-level structures of various molecules and also led to a series of spectroscopic applications in, for example, biomedicine, environmental monitoring, and combustion diagnostics. Nanosecond pulsed optical parametric sources tunable in the mid-IR are versatile tools offering the potential to access different molecular transitions. Their compact size and relatively high pulse energy allow convenient and sensitive detection in various types of spectroscopy.
Achievable narrow linewidths close to Fourier transform limit also make it possible to resolve Doppler-limited fine absorption lines and distinguish different species with high selectivity. As such, this thesis aims at the further development of pulsed optical parametric sources in the mid-IR region, employing different nonlinear materials and down-conversion configurations, as well as their application towards high-resolution molecular spectroscopy.
We have demonstrated optical parametric generation (OPG) in the newly invented nonlinear crystal, orientation-patterned gallium phosphide (OP-GaP). Pumped by a Q-switched Nd:YAG laser, the OPG source at 25 kHz repetition rate generates tunable radiation across 1721-1850 nm and 2504-2787 nm. Detailed characterization including temperature tuning, pump transmission, and OPG threshold validated the performance of OP-GaP as the next-generation quasi-phase-matched nonlinear material.
Following the development of the OPG, we further successfully demonstrated and characterized a singly-resonant optical parametric oscillator (OPO) based on OP-GaP. Driven by the same Nd:YAG laser at 50 kHz repetition rate, the OPO delivers mid-IR idler in the spectral range of 2.8-3.1 µm. Absorption-induced thermal effects in the OP-GaP sample were revealed and studied using different pump power levels.
We also demonstrated a stable, pulsed degenerate OPO at 2.1 µm based on MgO:PPLN and pumped by the same Nd:YAG laser with variable repetition rates from 65 kHz to 90 kHz. The OPO, in a Littrow-grating-cavity configuration, can provide up to 2.7 W of degenerate output with good pulse-to-pulse and long-term power stability. The spectral narrowing effect of the grating-cavity was also examined and compared to a plane-mirror linear cavity. Finally, we developed a high-resolution difference-frequency spectrometer in the spectral range of 3308.5-3317.3 nm. The mid-IR source for the spectrometer was based on single-frequency, mode-hop-free tunable, pulsed difference-frequency-generation (DFG) in MgO:PPLN. A part of the methane spectrum in the Q-branch of v3-band was resolved and compared to HITRAN simulation in both atmospheric pressure and reduced pressure. This conceptual technique can be extended to broader mid-IR regions for detecting various other molecules or to higher energy level for nonlinear spectroscopy with high resolution.
Friday, May 3, 15:00. ICFO Auditorium
Thesis Advisor: Prof Dr Majid Ebrahim Zadeh
Thesis Co-advisor: Dr Chaitanya K. Suddapalli
ICFO-The Institute of Photonic Sciences
The mid-infrared (mid-IR) spectral region coincides with fundamental rotational-vibrational transitions of a large number of molecules in the gas phase. The strong interaction between mid-IR light sources and these gaseous molecules has enabled experimental investigations of energy-level structures of various molecules and also led to a series of spectroscopic applications in, for example, biomedicine, environmental monitoring, and combustion diagnostics. Nanosecond pulsed optical parametric sources tunable in the mid-IR are versatile tools offering the potential to access different molecular transitions. Their compact size and relatively high pulse energy allow convenient and sensitive detection in various types of spectroscopy.
Achievable narrow linewidths close to Fourier transform limit also make it possible to resolve Doppler-limited fine absorption lines and distinguish different species with high selectivity. As such, this thesis aims at the further development of pulsed optical parametric sources in the mid-IR region, employing different nonlinear materials and down-conversion configurations, as well as their application towards high-resolution molecular spectroscopy.
We have demonstrated optical parametric generation (OPG) in the newly invented nonlinear crystal, orientation-patterned gallium phosphide (OP-GaP). Pumped by a Q-switched Nd:YAG laser, the OPG source at 25 kHz repetition rate generates tunable radiation across 1721-1850 nm and 2504-2787 nm. Detailed characterization including temperature tuning, pump transmission, and OPG threshold validated the performance of OP-GaP as the next-generation quasi-phase-matched nonlinear material.
Following the development of the OPG, we further successfully demonstrated and characterized a singly-resonant optical parametric oscillator (OPO) based on OP-GaP. Driven by the same Nd:YAG laser at 50 kHz repetition rate, the OPO delivers mid-IR idler in the spectral range of 2.8-3.1 µm. Absorption-induced thermal effects in the OP-GaP sample were revealed and studied using different pump power levels.
We also demonstrated a stable, pulsed degenerate OPO at 2.1 µm based on MgO:PPLN and pumped by the same Nd:YAG laser with variable repetition rates from 65 kHz to 90 kHz. The OPO, in a Littrow-grating-cavity configuration, can provide up to 2.7 W of degenerate output with good pulse-to-pulse and long-term power stability. The spectral narrowing effect of the grating-cavity was also examined and compared to a plane-mirror linear cavity. Finally, we developed a high-resolution difference-frequency spectrometer in the spectral range of 3308.5-3317.3 nm. The mid-IR source for the spectrometer was based on single-frequency, mode-hop-free tunable, pulsed difference-frequency-generation (DFG) in MgO:PPLN. A part of the methane spectrum in the Q-branch of v3-band was resolved and compared to HITRAN simulation in both atmospheric pressure and reduced pressure. This conceptual technique can be extended to broader mid-IR regions for detecting various other molecules or to higher energy level for nonlinear spectroscopy with high resolution.
Friday, May 3, 15:00. ICFO Auditorium
Thesis Advisor: Prof Dr Majid Ebrahim Zadeh
Thesis Co-advisor: Dr Chaitanya K. Suddapalli