This thesis presents a Kerr-lens mode-locked chromium-doped zinc selenide (Cr2+: ZnSe) laser at room temperature pumped with thulium-doped fiber at 1940 nm. The Cr2+: ZnSe medium offers a broadband gain bandwidth, thus, offering ultrafast pulse generation in the mid-infrared regime, as it is diode-pumped. The principal objective, here, is to acquire the shortest pulse duration of mode-locked pulses with maximum intracavity gain efficiency, while keeping the loss due to the alignment of the optical elements and several factors, such as astigmatism, minimum. In this sense, the experiment is constructed upon the basis of an X-folded laser cavity with a 3% output coupler, from which at 150 MHz, the shortest pulse is received as 59.7 fs, equivalent to 11 − 12 optical cycles with an output power of 177 mW. Additionally, the widest gain bandwidth is obtained as 6 THz with a central wavelength of 2389 nm. The results reveal the fact that even shorter pulses can be reached if the dispersion and temperature control are re-visioned. Moreover, the effect of water absorption lines in the atmosphere on the laser action is notably observed when the central emission wavelength is beyond 2400 nm, which makes the mode-locking action more difficult in higher wavelengths.
Questa tesi presenta un laser in mode-locking a effetto Kerr basato su un mezzo attivo in Seleniuro di Zinco drogato Cromo (Cr2+: ZnSe) pompato da un laser in fibra al Tullio a 1940 nm. Il Cr2+: ZnSe offre una larga banda di guadagno nel medio infrarosso, cosi da permettere la generazione di impulsi ultrabrevi quando è pompato otticamente. Qui, il principale obiettivo è di ottenere i più brevi impulsi possibili in regime di mode-locking, con la massima efficienza di guadagno intracavità, mantenendo le perdite dovute a elementi ottici e altri fattori, come l’astigmatismo, al minimo. In questo senso, l’esperimento è costruito sulla base di una cavità laser piegata a X con un accordatore di uscita al 3%, dalla quale, a 150 MHz, è stato misurato un impulso a 59.7 fs, equivalente a 11 − 12 cicli ottici, con una potenza media di uscita di 177 mW. Inoltre, la massima banda di guadagno è stata misurata a 2389 nm con una larghezza di 6 THz. I risultati rivelano che impulsi ancora più corti possono essere generati se i controlli di temperatura e dispersione fossero revisionati. Più di questo, l’effetto delle linee di assorbimento dell’acqua nell’atmosfera si osserva sull’azione del laser, in particolare, quando la lunghezza d’onda di emissione è superiore a 2400 nm, il che rende più difficile l’azione in mode-locking a lunghezze d’onda più elevate.
Femtosecond Kerr-lens mode-locked Cr2+:ZnSe laser
Erdem, Ugur Can
2019/2020
Abstract
This thesis presents a Kerr-lens mode-locked chromium-doped zinc selenide (Cr2+: ZnSe) laser at room temperature pumped with thulium-doped fiber at 1940 nm. The Cr2+: ZnSe medium offers a broadband gain bandwidth, thus, offering ultrafast pulse generation in the mid-infrared regime, as it is diode-pumped. The principal objective, here, is to acquire the shortest pulse duration of mode-locked pulses with maximum intracavity gain efficiency, while keeping the loss due to the alignment of the optical elements and several factors, such as astigmatism, minimum. In this sense, the experiment is constructed upon the basis of an X-folded laser cavity with a 3% output coupler, from which at 150 MHz, the shortest pulse is received as 59.7 fs, equivalent to 11 − 12 optical cycles with an output power of 177 mW. Additionally, the widest gain bandwidth is obtained as 6 THz with a central wavelength of 2389 nm. The results reveal the fact that even shorter pulses can be reached if the dispersion and temperature control are re-visioned. Moreover, the effect of water absorption lines in the atmosphere on the laser action is notably observed when the central emission wavelength is beyond 2400 nm, which makes the mode-locking action more difficult in higher wavelengths.File | Dimensione | Formato | |
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Descrizione: Femtosecond Kerr-lens mode-locked Cr:ZnSe laser
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https://hdl.handle.net/10589/173257