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Optical Pulse Shaping For Chirped Pulse Interferometry And Bio-ImagingSchreiter, Kurt January 2011 (has links)
Biomedical imaging requires high resolution to see the fine features of a sample and
fast acquisition to observe live cells that move. Optical coherence tomography (OCT) is
a powerful technique which uses optical interference for non-invasive high resolution 3D
imaging in biological samples.
The resolution of OCT is determined by the length over which the light used will in-
terfere. Unfortunately, dispersion hurts the imaging resolution by broadening interference
features. A technique called quantum-OCT (QOCT)[1] is immune to dispersion but re-
quires entangled photon pairs. The need for entanglement drastically reduces the number
of photons available for imaging, making QOCT too slow to be practical. Chirped-pulse
interferometry (CPI) is also immune to dispersion. A chirped pulse is one where the fre-
quency, or colour, of the light changes from red to blue from one end of the pulse to the
other. CPI relies on frequency correlations created by applying different chirps to two sep-
arate pulses. This method had the disadvantage of being limited to a single predetermined
chirp rate, and discarded 50% of the power. However CPI has better resolution than OCT,
automatic dispersion cancellation, and 10,000,000 times the signal strength of QOCT [13].
A new, much more flexible and efficient method of CPI will be demonstrated by creating
the frequency correlations entirely in a single pulse. This new method is referred to as non-
linear chirped pulse interferometry (NL-CPI).
The non-linear chirp required in NCPI is very difficult to produce using only conven-
tional optics. In this thesis we document the construction and characterization of a new
method of creating the desired chirp using a programmable pulse-shaper (PS). We build a
PPS and then demonstrated its functionality by compressing a 105nm FWHM bandwidth
pulse to under 17f s, near its transform limited time duration. We also show that the
values given to the PPS for dispersion are accurate by calculating and then compensating
the dispersion caused by various optical elements in the CPI interferometer.
Conventional OCT systems are immune to dispersion common to both arms of the
interferometer. Non-linear interferometers experience broadening due to this dispersion,
making them more difficult to use with fibre based interferometers common in conventional
OCT. We show that NL-CPI can compensate for dispersion common to both arms of the
interferometer, making NL-CPI more appealing as a replacement for conventional OCT.
In this thesis we experimentally implement and demonstrate a prototype setup using
non-linear CPI for dispersion-cancelled imaging of a mirror, with a resolution comparable
to conventional OCT systems. We then use the system to produce 2-D cross sectional
images of a biological sample, an onion. Q-OCT has previously been used to image an
onion[16], but required treating the onion with gold nano particles to achieve a useful
signal. The onion we used had no special treatment. In addition our axial scanning rate
is also 10000 times faster than Q-OCT.
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Optical Pulse Shaping For Chirped Pulse Interferometry And Bio-ImagingSchreiter, Kurt January 2011 (has links)
Biomedical imaging requires high resolution to see the fine features of a sample and
fast acquisition to observe live cells that move. Optical coherence tomography (OCT) is
a powerful technique which uses optical interference for non-invasive high resolution 3D
imaging in biological samples.
The resolution of OCT is determined by the length over which the light used will in-
terfere. Unfortunately, dispersion hurts the imaging resolution by broadening interference
features. A technique called quantum-OCT (QOCT)[1] is immune to dispersion but re-
quires entangled photon pairs. The need for entanglement drastically reduces the number
of photons available for imaging, making QOCT too slow to be practical. Chirped-pulse
interferometry (CPI) is also immune to dispersion. A chirped pulse is one where the fre-
quency, or colour, of the light changes from red to blue from one end of the pulse to the
other. CPI relies on frequency correlations created by applying different chirps to two sep-
arate pulses. This method had the disadvantage of being limited to a single predetermined
chirp rate, and discarded 50% of the power. However CPI has better resolution than OCT,
automatic dispersion cancellation, and 10,000,000 times the signal strength of QOCT [13].
A new, much more flexible and efficient method of CPI will be demonstrated by creating
the frequency correlations entirely in a single pulse. This new method is referred to as non-
linear chirped pulse interferometry (NL-CPI).
The non-linear chirp required in NCPI is very difficult to produce using only conven-
tional optics. In this thesis we document the construction and characterization of a new
method of creating the desired chirp using a programmable pulse-shaper (PS). We build a
PPS and then demonstrated its functionality by compressing a 105nm FWHM bandwidth
pulse to under 17f s, near its transform limited time duration. We also show that the
values given to the PPS for dispersion are accurate by calculating and then compensating
the dispersion caused by various optical elements in the CPI interferometer.
Conventional OCT systems are immune to dispersion common to both arms of the
interferometer. Non-linear interferometers experience broadening due to this dispersion,
making them more difficult to use with fibre based interferometers common in conventional
OCT. We show that NL-CPI can compensate for dispersion common to both arms of the
interferometer, making NL-CPI more appealing as a replacement for conventional OCT.
In this thesis we experimentally implement and demonstrate a prototype setup using
non-linear CPI for dispersion-cancelled imaging of a mirror, with a resolution comparable
to conventional OCT systems. We then use the system to produce 2-D cross sectional
images of a biological sample, an onion. Q-OCT has previously been used to image an
onion[16], but required treating the onion with gold nano particles to achieve a useful
signal. The onion we used had no special treatment. In addition our axial scanning rate
is also 10000 times faster than Q-OCT.
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Synchronization In Advanced Optical CommunicationsKim, Inwoong 01 January 2006 (has links)
The objective of this dissertation is to generate high power ultrashort optical pulses from an all-semiconductor mode-locked laser system. The limitations of semiconductor optical amplifier in high energy, ultrashort pulse amplification are reviewed. A method to overcome the fundamental limit of small stored energy inside semiconductor optical amplifier called "eXtreme Chirped Pulse Amplification (X-CPA)" is proposed and studied theoretically and experimentally. The key benefits of the concept of X-CPA are addressed. Based on theoretical and experimental study, an all-semiconductor mode-locked X-CPA system consisting of a mode-locked master oscillator, an optical pulse pre-stretcher, a semiconductor optical amplifier (SOA) pulse picker, an extreme pulse stretcher/compressor, cascaded optical amplifiers, and a bulk grating compressor is successfully demonstrated and generates >kW record peak power. A potential candidate for generating high average power from an X-CPA system, novel grating coupled surface emitting semiconductor laser (GCSEL) devices, are studied experimentally. The first demonstration of mode-locking with GCSELs and associated amplification characteristics of grating coupled surface emitting SOAs will be presented. In an effort to go beyond the record setting results of the X-CPA system, a passive optical cavity amplification technique in conjunction with the X-CPA system is constructed, and studied experimentally and theoretically.
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Terawatt Raman laser system for two-color laser plasma interactionsSanders, James Christopher 18 September 2014 (has links)
In some high-field laser-plasma experiments, it is advantageous to accompany the main high-energy (~1 J) laser with a second high-energy pulse (~0.1 J) which has been frequency-shifted by ~10-20%. Such a pulse-pair would have a low walk-off velocity while remaining spectrally distinct for use in two-color pump-probe experiments. Moreover, by shifting the second pulse by ~plasma frequency, it is theoretically possible to exercise some amount of control over a variety of laser-plasma instabilities, including forward Raman scattering, electromagnetic cascading, and relativistic self-focusing. Alternatively, the two pulses may be counter-propagated so that the collide in the plasma and create a slowly-propagating beatwave which can be used to inject electrons into a laser wakefield accelerator. The design, characeterization, and performance of a hybrid chirped-pulse Raman amplifier (CPRA)/Ti-Sapphire amplifier are reported and discussed. This hybrid system allows for the generation of a high-energy (>200 mJ), broadband (15-20 nm bandwidth FWHM), short duration (>100 fs duration) laser sideband. When amplified and compressed, the Raman beam's power exceeds 1 TW. This sideband is combined with the primary laser system to create a bi-color terawatt laser system which is capable of performing two-color high-field experiments. This two-color capability can be added to any commercial terawatt laser system without compromising the energy, duration or beam quality of the primary system. Preliminary two-color laser-plasma experiments are also discussed. / text
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BROADBAND MICROWAVE SPECTROSCOPY OF LIGNIN, BIOFUELS AND THEIR PYROLYSIS INTERMEDIATESAlicia O. Hernandez-Castillo (5929736) 03 January 2019 (has links)
<div>The chemical complexity of hydrocarbon fuels and the fast-expanding list of potential plantderived biofuels pose a challenge to the scientific community seeking to provide a molecular understanding of their combustion. More refined spectroscopic tools and methodologies must be developed to selectively detect and characterize the widening array of fuel components and combustion reactive intermediates. The direct relationship between molecular structure and rotational frequencies makes rotational spectroscopy highly structural specific; therefore, it offers a powerful means of characterizing pyrolysis ntermediates. This thesis describes experimental work using broadband microwave spectroscopy to address a number of challenging problems in the spectroscopy of gas complex mixtures.</div><div><br></div><div>Usually, the observed rotational spectra contain contributions from many distinct species, creating a complicated spectrum with interleaved transitions that make spectral assignment challenging. To assist with the process, a protocol called “strong-field coherence breaking” (SFCB) has been developed. It exploits multi-resonance effects that accompany sweeping the microwave radiation under strong-field conditions to output a set of transitions that can confidently be assigned to a single component in a mixture, thereby reducing the spectral assignment time.</div><div><br></div><div>The broadband chirped pulse Fourier transform microwave (CP-FTMW) spectra of guaiacol, syringol, 4-methyl guaiacol, 4-vinyl guaiacol were recorded under jet- cooled conditions over the 2-18 GHz frequency range. Using data from the 13C isotopomers the r0 structure of guaiacol was determined by means of a Kraitchman analysis. The tunneling due to OH hindered rotation was observed in syringol and the V2 barrier was deduced to be 50% greater than phenol’s barrier. This is due to the intramolecular H-bonding between the hydroxy and the methoxy groups. The internal rotation barrier for the methyl group for 4-methyl guaiacol was also determined. Moreover, the spectral assignment of the two conformers of 4-vinyl guaiacol was sped-up by using SFCB. The main structural insight from these lignin-related molecules was that polar substituents dictate the magnitude and type of structural shift that occurs relative to that of the unsubstituted aromatic ring.</div><div><br></div><div>In the next part of my work, the pyrolysis of 2-methoxy furan was carried out over the 300-1600 K temperature range, with microwave detection in the 2-18 GHz frequency range, using hightemperature flash pyrolysis micro-reactor coupled with a supersonic expansion. The SFCB technique was used to analyze and speed up the line assignment. The 2-furanyloxy radical, a primary, resonance-stabilized radical formed by loss of a methyl group in the pyrolysis of 2-methoxy furan, was detected and its molecular parameters were determined.</div><div><br></div><div>Finally, a unique setup that combines the high-resolution spectroscopic data provided by chirped pulse Fourier transform microwave (CP-FTMW) spectroscopy with photoionization mass spectra from a vacuum ultraviolet (VUV) time-of-flight mass spectrometer (TOF-MS) was used to find optimal conditions to detect reactive intermediates and make full assignments for the microwave spectra of phenoxy radical and o-hydroxy phenoxy radical over the 2-18 GHz range. Phenoxy radical was generated through the pyrolysis of anisole and allyl phenyl ether. Using a combination of data from 13C isotopomers and fully deuterated phenoxy radical, in combination with high level ab initio calculations, a near-complete r0 structure for the radical was obtained. The structural data point to the radical being a primarily carbon-centered rather than oxygencentered radical. Using guaiacol as precursor, we studied the spectroscopy of the o-hydroxy phenoxy radical, whose structural data is compared with that of phenoxy to understand the role played by the hydroxyl group in modifying the resonance stabilization of the radical.</div><div><br></div>
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Real-time Interrogation of Fiber Bragg Grating Sensors Based on Chirped Pulse CompressionLiu, Weilin 05 October 2011 (has links)
Theoretical and experimental studies of real-time interrogation of fiber Bragg grating (FBG) sensors based on chirped pulse compression with increased interrogation resolution and signal-to-noise ratio are presented. Two interrogation systems are proposed in this thesis.
In the first interrogation system, a linearly chirped FBG (LCFBG) is employed as the sensing element. By incorporating the LCFBG in an optical interferometer as the sensor encoding system, employing wavelength-to-time mapping and chirped pulse compression technique, the correlation of output microwave waveform with a chirped reference waveform would provide an interrogation result with high speed and high resolution. The proposed system can provide an interrogation resolution as high as 0.25 μ at a speed of 48.6 MHz. The second interrogation system is designed to achieve simultaneous measurement of strain and temperature. In this system, a high-birefringence LCFBG (Hi-Bi LCFBG) is employed as a sensing element.
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Real-time Interrogation of Fiber Bragg Grating Sensors Based on Chirped Pulse CompressionLiu, Weilin 05 October 2011 (has links)
Theoretical and experimental studies of real-time interrogation of fiber Bragg grating (FBG) sensors based on chirped pulse compression with increased interrogation resolution and signal-to-noise ratio are presented. Two interrogation systems are proposed in this thesis.
In the first interrogation system, a linearly chirped FBG (LCFBG) is employed as the sensing element. By incorporating the LCFBG in an optical interferometer as the sensor encoding system, employing wavelength-to-time mapping and chirped pulse compression technique, the correlation of output microwave waveform with a chirped reference waveform would provide an interrogation result with high speed and high resolution. The proposed system can provide an interrogation resolution as high as 0.25 μ at a speed of 48.6 MHz. The second interrogation system is designed to achieve simultaneous measurement of strain and temperature. In this system, a high-birefringence LCFBG (Hi-Bi LCFBG) is employed as a sensing element.
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Timing Issues In A Terawatt Laser SystemYilmaz, Remziye Pinar 01 September 2008 (has links) (PDF)
In the laser market, there have been various kinds of lasers designed and utilized for
different purposes. As time goes on, their powers have been gradually increased
from kilowatts (kW) to terawatts (TW). One of the most famous methods in laser
science technology is Chirped Pulse Amplification (CPA) which enables table-top
terawatt laser systems. This method provides high output power (tens of TW), very
short pulse duration (few tens of femtoseconds) and large energy (mJ) for ultrafast
lasers. One of the most well-known ultrafast lasers is Titanium:Sapphire laser. This
thesis work concentrates on how delay a pulse generator should work so that Verdi
and the oscillator pulse coincide. Moreover, by assembling a terawatt laser system,
the most important issues are timing between seed pulse and pump pulse and time
delays of all components of this system / autocorrelator, pump source, photodiode,
Pockels cell, stretcher and dazzler were examined. This timing and the time delays
were separately identified for terawatt laser systems. In this study, the aim is to
attain the terawatt level output by arranging pump and seed pulses timing and the
time delay on the components of the laser system setup.
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High energy broad bandwidth optical parametric chirped pulse amplification / Didelės išvadinės energijos plataus spektro čirpuotų impulsų optinis parametrinis stiprinimasAntipenkov, Roman 07 March 2011 (has links)
Rapidly developing areas of high field physics, generation of high order harmonics or isolated attosecond pulses, require high peak power few-cycle pulse sources. Optical parametric chirped pulse amplification (OPCPA) has shown potential to satisfy these requirements and at present OPCPA is the leading technology for high energy few-cycle pulse table-top systems.
The main objectives of this thesis were to investigate optical parametric amplification of broadband seed pulses in femtosecond and picosecond regimes, to develop and optimize a compact TW-scale OPCPA system intended for various applications in areas of high-field physics. In this thesis the main concept of such system is discussed, advantages and disadvantages of proposed approach are analyzed, the setup is compared to other world known systems.
In this thesis an original approach for power scaling of regenerative amplifier by implementing several active elements in prolonged resonator has been proposed and investigated. Femtosecond pulse amplification in dual active element Yb:KGW regenerative amplifier has been demonstrated, resulting in boost of average output power to 30 W.
Broad bandwidth pulse generation, parametric amplification and compression to transform limited values were analyzed both numerically and experimentally. White light continuum generation in bulk material for broadband seed formation, its further optical parametric amplification in noncollinear scheme were investigated and Yb:KGW driven... [to full text] / Stiprių laukų fizikos srities tyrimams, aukštų eilių harmonikų ir pavienių atosekundinių impulsų generavimui, yra reikalingos kompaktiškos teravatų smailinės galios kelių optinių ciklų išvadinių impulsų lazerinės sistemos. Optinis parametrinis „čirpuotų“ impulsų stiprinimas yra vienas pagrindinių metodų leidžiančiu pasiekti šiems taikymams reikalingus lazerinių sistemų parametrus.
Šios disertacijos darbo tikslas – ištirti femtosekundinės ir pikosekundinės trukmės impulsų stiprinimą optiniuose parametriniuose stiprintuvuose užkratui naudojant ypač plataus spektro signalą, bei sukurti ir optimizuoti čirpuotų impulsų parametrinio stiprinimo sistemą, užtikrinančią patikimą teravatų smailinės galios impulsų formavimą. Disertacijoje aptariama bendra tokios sistemos architektūra, nagrinėjami privalumai ir trūkumai, palyginama su kitomis pasaulyje egzistuojančiomis sistemomis.
Šiame darbe pasiūlytas ir ištirtas lazerių vidutinės išvadinės galios didinimo metodas, naudojant kelis aktyviuosius elementus viename rezonatoriuje, ir pademonstruotas femtosekundinių impulsų stiprinimas šio metodo pagrindu sukonstruotame dviejų Yb:KGW aktyvių elementų regeneratyviniame stiprintuve, tokiu būdu padidinant lazerio išvadinę galią iki 30 W.
Darbo metu sukonstruota bei ištirta Yb:KGW femtosekundiniu lazeriu kaupinamos baltos šviesos kontinuumo generavimo ir nekolinearaus kaupinimo optinio parametrinio stiprinimo sistema, kurios išvadinių impulsų energiją siekia 20 mikrodžiaulių, o impulsai... [toliau žr. visą tekstą]
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Real-time Interrogation of Fiber Bragg Grating Sensors Based on Chirped Pulse CompressionLiu, Weilin 05 October 2011 (has links)
Theoretical and experimental studies of real-time interrogation of fiber Bragg grating (FBG) sensors based on chirped pulse compression with increased interrogation resolution and signal-to-noise ratio are presented. Two interrogation systems are proposed in this thesis.
In the first interrogation system, a linearly chirped FBG (LCFBG) is employed as the sensing element. By incorporating the LCFBG in an optical interferometer as the sensor encoding system, employing wavelength-to-time mapping and chirped pulse compression technique, the correlation of output microwave waveform with a chirped reference waveform would provide an interrogation result with high speed and high resolution. The proposed system can provide an interrogation resolution as high as 0.25 μ at a speed of 48.6 MHz. The second interrogation system is designed to achieve simultaneous measurement of strain and temperature. In this system, a high-birefringence LCFBG (Hi-Bi LCFBG) is employed as a sensing element.
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