Gain flattening filter for preserving the spectral bandwidth in cryogenic ultrashort-pulse laser amplifiers

Abstract

A gain flattening filter preserves very broad bandwidth, and therefore very short-duration pulses in ultrafast cryogenically-cooled laser amplifier systems, while also maintaining good overall efficiency. The filter is optimized for pulses amplified in a cryogenically cooled material.

Description

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 60 / 706,389, filed Aug. 8, 2005.BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to gain flattening filters for use in laser amplifiers. In particular, this invention relates to gain flattening filters optimized for use in cryogenic ultrashort-pulse laser amplifiers.

[0004] 2. Description of Related Art

[0005] Gain narrowing has long been recognized as a problem in amplifiers where the beam passes through the amplifying medium multiple times (e.g. multipass configurations and regenerative configurations). Both multipass and regenerative amplifiers pass the beam being amplified through the gain material a number of times, in order to achieve sufficient amplification. Since gain follows a generally bell-shaped curve, the repeated passes result not just in increased power, but also in narrowed gain profile. Since the pulse duration and spectral bandwidth have a...

Examples

Embodiment Construction

[0030]FIG. 2 is a block diagram of a preferred embodiment of a cryogenically cooled ultrafast ti:sapphire laser amplifier 100 using a gain flattening filter 122. The embodiment of FIG. 2 is a “multipass” amplifier configuration, wherein the beam shifts slightly in path with each pass, which allows the inclusion of an optional feature wherein filter 122 intersects the beam path for a variable number of passes—i.e. it intersects the first several passes 128, but the last several passes 126 bypass the filter. The final pass intersects output mirror 132 and is diverted out of the amplifier as output pulse 134.

[0031] Ultrafast laser amplifier system 100 takes an ultrashort light pulse 102, “stretches” it in time, then puts the beam through an amplification process that typically requires 8-20 passes through a laser crystal 114 to increase the output pulse 134 energy from ˜10−9 Joules to ˜10−3 J or higher. Pump beam 101 enters the system at the right in FIG. 2.

[0032] Input beam 102 refl...

[0001] This application claims the benefit of U.S. Provisional Patent Application No. 60 / 706,389, filed Aug. 8, 2005.BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to gain flattening filters for use in laser amplifiers. In particular, this invention relates to gain flattening filters optimized for use in cryogenic ultrashort-pulse laser amplifiers.

[0004] 2. Description of Related Art

[0005] Gain narrowing has long been recognized as a problem in amplifiers where the beam passes through the amplifying medium multiple times (e.g. multipass configurations and regenerative configurations). Both multipass and regenerative amplifiers pass the beam being amplified through the gain material a number of times, in order to achieve sufficient amplification. Since gain follows a generally bell-shaped curve, the repeated passes result not just in increased power, but also in narrowed gain profile. Since the pulse duration and spectral bandwidth have a...

Examples

Embodiment Construction

[0030]FIG. 2 is a block diagram of a preferred embodiment of a cryogenically cooled ultrafast ti:sapphire laser amplifier 100 using a gain flattening filter 122. The embodiment of FIG. 2 is a “multipass” amplifier configuration, wherein the beam shifts slightly in path with each pass, which allows the inclusion of an optional feature wherein filter 122 intersects the beam path for a variable number of passes—i.e. it intersects the first several passes 128, but the last several passes 126 bypass the filter. The final pass intersects output mirror 132 and is diverted out of the amplifier as output pulse 134.

[0031] Ultrafast laser amplifier system 100 takes an ultrashort light pulse 102, “stretches” it in time, then puts the beam through an amplification process that typically requires 8-20 passes through a laser crystal 114 to increase the output pulse 134 energy from ˜10−9 Joules to ˜10−3 J or higher. Pump beam 101 enters the system at the right in FIG. 2.

[0032] Input beam 102 refl...

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