is it possible to generate attosecond pulses by using femtosecond set-up ? can you give me an experimental idea about this technique ?
Hello Sumit (and others) --
(I posted this answer in the other thread before seeing you had created a new one. Here I have copied the answer for the benefit of anyone else following the conversation.)
People use several different kinds of lasers for producing the femtosecond pulse durations needed to drive high harmonic generation. This is actually its own field of research: in addition to ubiquitous Ti:sapphire-based systems, many researchers have achieved truly remarkable results relevant to attoscience with laser architectures based on optical parametric chirped-pulse amplification (OPCPA) or chirped-pulse amplification (CPA) in fibers and other solid-state gain media. Of course, each type of laser has its advantages (e.g. repetition rate, pulse energy, wavelength) that may make it more suitable for certain applications over others.
Speaking specifically of Ti:sapphire lasers (which you had asked about previously), most current setups used for generating isolated attosecond pulses involve a femtosecond oscillator, a pulse stretcher, the amplifier itself (which may consist of regenerative or multi-pass configurations, or both), and a pulse compressor. Because of gain-narrowing due to amplification of the pulse energy from the ~nJ to the ~mJ level, the pulse duration is usually limited to >25 fs, which is too long for generating isolated attosecond pulses with most common gating methods. (Because it relates to my own research, I will mention that an exception to this rule of thumb is double optical gating (along with its variants), which allows isolated attosecond pulse generation with pulses directly from the amplifier and compressor. This method can also work without facing the challenges of carrier-envelope phase (CEP) stabilization, which is required for most few-cycle gating methods like amplitude gating and ionization gating.)
Because of the long pulse durations after the compressor, most typical setups use a hollow-core fiber or filamentation tube to generate an ultrabroadband spectrum (e.g. several hundred nm) through self-phase modulation (SPM). This spectrum can be compressed using ultrabroadband chirped mirrors down to pulse durations as short as
Hello Sumit (and others) --
(I posted this answer in the other thread before seeing you had created a new one. Here I have copied the answer for the benefit of anyone else following the conversation.)
People use several different kinds of lasers for producing the femtosecond pulse durations needed to drive high harmonic generation. This is actually its own field of research: in addition to ubiquitous Ti:sapphire-based systems, many researchers have achieved truly remarkable results relevant to attoscience with laser architectures based on optical parametric chirped-pulse amplification (OPCPA) or chirped-pulse amplification (CPA) in fibers and other solid-state gain media. Of course, each type of laser has its advantages (e.g. repetition rate, pulse energy, wavelength) that may make it more suitable for certain applications over others.
Speaking specifically of Ti:sapphire lasers (which you had asked about previously), most current setups used for generating isolated attosecond pulses involve a femtosecond oscillator, a pulse stretcher, the amplifier itself (which may consist of regenerative or multi-pass configurations, or both), and a pulse compressor. Because of gain-narrowing due to amplification of the pulse energy from the ~nJ to the ~mJ level, the pulse duration is usually limited to >25 fs, which is too long for generating isolated attosecond pulses with most common gating methods. (Because it relates to my own research, I will mention that an exception to this rule of thumb is double optical gating (along with its variants), which allows isolated attosecond pulse generation with pulses directly from the amplifier and compressor. This method can also work without facing the challenges of carrier-envelope phase (CEP) stabilization, which is required for most few-cycle gating methods like amplitude gating and ionization gating.)
Because of the long pulse durations after the compressor, most typical setups use a hollow-core fiber or filamentation tube to generate an ultrabroadband spectrum (e.g. several hundred nm) through self-phase modulation (SPM). This spectrum can be compressed using ultrabroadband chirped mirrors down to pulse durations as short as
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