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|Title: ||Solid state optical conjugated polymer amplifier; with ultrafast gain switching|
|Authors: ||Amarasinghe, Dimali C. V.|
|Supervisors: ||Samuel, Ifor D. W.|
|Issue Date: ||30-Nov-2008|
|Abstract: ||Conjugated polymers are organic materials which are attractive as optoelectronic devices
because they have a combination of broad band emission, high gain, versatility
in processing, are ductile and can be electrically pumped. This thesis describes work
conducted on such conjugated polymers as amplifier devices.
The conjugated polymers used in this thesis were MEH-PPV, F8BT, GP1302 and
ADS233YE. The amplifier devices used were grating coupled and end coupling waveguides.
Amplification of light was demonstrated and characterised on single and multiple
pulses using the grating coupled structure. Single pulse measurements obtained
gains of 21 and 17 dB in a 1 mm long waveguide using the conjugated polymers MEHPPV
and F8BT. Annihilation rate was also analysed in the single pulse method with
MEH-PPV, giving a value of
γ ≈ (3 ± 0.1) x 10⁻⁹ cm³/s.
Amplification of a single pulse led to demonstrate amplification and the capability
of the amplifier to function with multiple pulses, which resulted in F8BT being used
as the gain medium. An average gain of 18 dB was obtained with F8BT in a 1 mm
waveguide channel. Amplification was also investigated with end coupled waveguides.
This led into investigating a suitable material or suitable combination of material for
amplification with the waveguides.
Switching of an amplified pulse was attempted on F8BT and GP1302 in the amplifier
device at 5 kHz. Switching of F8BT was problematic which lead to attempt
switching in GP1302 which was a co-polymer of PFO and F8BT. A 70 % switching
effect was obtained with GP1302. Gain recovery dynamics of F8BT, GP1302 and
ADS233YE was also investigated. These measurements established a switching rate
of 500 GHz for GP1302 and ADS233YE, and F8BT showed partial gain recovery
indicating the presence of long lived species.
Switching was also attempted on a polymer laser. This resulted in a 100 % switched
pulse with a combination of weak pump and strong switch pulse of 40 nJ and 2 μJ
respectively. And a strong pump and weak switch pulse of 200 and 50 nJ respectively.
Temporal delay of the switch pulse relative to the pump pulse resulted in re-timing
of the laser output. Amplification and switching of light pulses were also attempted at a higher repetition
rate of 50 kHz with F8BT, GP1302, ADS233YE and MEH-PPV. This resulted
in strong amplification of light in MEH-PPV and F8BT with gains of 21 and 13
dB respectively in a waveguide length of 422 μm. Weak amplification of light in
ADS233YE and GP1302 was also obtained with a maximum gain of 8 and 3 dB
respectively. Switching was attempted on MEH-PPV and ADS233YE.|
|Publisher: ||University of St Andrews|
|Appears in Collections:||Physics & Astronomy Theses|
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