Systematic analysis of an attosecond pulse generation by a subcycle laser field
Rambabu Rajpoot, Eiji J. Takahashi
Abstract
We investigated the influence of subcycle driving fields on high-order harmonic generation (HHG), with a focus on driver's intrinsic chirp, carrier-envelope phase (CEP), and number of laser cycles. Our findings reveal that the center frequency of a laser pulse scales as <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"> <a:msup> <a:mi>τ</a:mi> <a:mrow> <a:mo>−</a:mo> <a:mn>5</a:mn> <a:mo>/</a:mo> <a:mn>4</a:mn> </a:mrow> </a:msup> </a:math> with pulse duration <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"> <b:mi>τ</b:mi> </b:math> , and that attochirp exhibits a similar dependence on pulse duration. Additionally, we identified CEP-specific trends in harmonic yield: it increases as <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"> <c:msup> <c:mi>τ</c:mi> <c:mrow> <c:mn>5</c:mn> <c:mo>/</c:mo> <c:mn>4</c:mn> </c:mrow> </c:msup> </c:math> for <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"> <d:mrow> <d:msub> <d:mi>ϕ</d:mi> <d:mn>0</d:mn> </d:msub> <d:mo>=</d:mo> <d:msup> <d:mn>0</d:mn> <d:mo>∘</d:mo> </d:msup> </d:mrow> </d:math> and decreases as <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"> <e:msup> <e:mi>τ</e:mi> <e:mrow> <e:mo>−</e:mo> <e:mn>4.1</e:mn> </e:mrow> </e:msup> </e:math> for <f:math xmlns:f="http://www.w3.org/1998/Math/MathML"> <f:mrow> <f:msub> <f:mi>ϕ</f:mi> <f:mn>0</f:mn> </f:msub> <f:mo>=</f:mo> <f:mo>−</f:mo> <f:msup> <f:mn>90</f:mn> <f:mo>∘</f:mo> </f:msup> </f:mrow> </f:math> . Although subcycle pulses can generate intense isolated attosecond pulses (IAPs), they also tend to produce higher attochirp and reduced cutoff energies. However, effective compensation for attochirp can mitigate these drawbacks, thereby increasing the capability of subcycle pulses to generate short-duration, high-intensity IAPs. These results offer valuable insights into HHG using subcycle pulses and have important implications for the advancement of ultrafast light sources and the understanding of ultrafast phenomena at the attosecond timescale.