A precision apparatus for high harmonic spectroscopy in bulk solids

TL;DR

This paper introduces a highly precise and stable apparatus for high harmonic generation spectroscopy in bulk solids, enabling detailed ultrafast electron and band structure studies with broad spectral detection and accurate field calibration.

Contribution

The authors developed an integrated, versatile system for quantitative HHG measurements in solids, combining advanced stabilization, broadband detection, and absolute electric field calibration.

Findings

Achieved stable, high-accuracy HHG measurements in bulk solids.

Enabled broadband UV to EUV harmonic detection with spatial filtering.

Provided a platform for reconstructing electronic structures and ultrafast dynamics.

Abstract

High harmonic generation (HHG) in solids has emerged as a powerful spectroscopic method for resolving ultrafast electron dynamics and band structure properties across a wide range of materials. However, quantitative HHG studies require instrumentation capable of delivering stable driving fields, precise crystal alignment, and broadband detection spanning the UV to the extreme ultraviolet (EUV). Here we present an integrated apparatus engineered specifically for high-accuracy, field-strength and orientation-dependent HHG measurements in bulk solids. The system incorporates dispersion-neutral intensity-control for few-cycle pulses, a vacuum HHG module with sub-micrometer and sub-degree sample positioning, and an imaging assembly that stabilizes the focal spot position and enables spatial filtering of the emitted harmonics. A synchronized dual-spectrometer scheme provides simultaneous UV/VUV and EUV radiation detection, while absolute electric field calibration is achieved through gas-phase attosecond streaking. Together, these capabilities establish a versatile and quantitatively reliable platform for solid-state HHG spectroscopy. The methodology is broadly adaptable to various laser sources and material classes, and supports future efforts aimed at reconstructing valence-electron potentials, tracking strong-field dynamics, and mapping electronic structure with sub-cycle temporal resolution.