Harmonic holography: a new holographic principle

Abstract

The process of second harmonic generation (SHG) has a unique property of forming a sharp optical contrast between noncentrosymmetric crystalline materials and other types of material, which is a highly valuable asset for contrast microscopy. The coherent signal obtained through SHG also allows for the recording of holograms at high spatial and temporal resolution, enabling whole-field four-dimensional microscopy for highly dynamic microsystems and nanosystems. Here we describe a new holographic principle, harmonic holography ͑H 2 ͒, which records holograms between independently generated second harmonic signals and reference. We experimentally demonstrate this technique with digital holographic recording of second harmonic signals upconverted from an ensemble of second harmonic generating nanocrystal clusters under femtosecond laser excitation. Our results show that harmonic holography is uniquely suited for ultrafast four-dimensional contrast microscopy.

Three-dimensional harmonic holographic microcopy using nanoparticles as probes for cell imaging

“…The peak intensity of the excitation is 1.5 GW/cm 2 , which is 100 times less than the cell damage threshold [33] and is also 100 times less than that used in Ref. 10. The experimental setup is shown in Fig.…”

“…The collection efficiency of the SHG signal was ~1%, which could also be significantly improved by adapting the optics for the SHG frequency. Moreover, the reference beam in holography can serve as a coherent local oscillator, leading to a gain in signal to noise ratio and a shot noise-limited performance of detection even at fast read-out [10]. As a pulsed holographic technique, the H 2 microscopy could reach a temporal resolution limited by the laser pulse width [10,36].…”

“…This also results in the flexibility of tuning the wavelength of the SHG signal by changing the excitation wavelength accordingly. The coherent nature of the SHG signal is also a main advantage, providing a possibility to detect the second harmonic signal with interferometric optical techniques [10][11][12][13].…”

“…The principle of harmonic holography was recently demonstrated [10]. When the digital hologram is recorded at the doubled frequency, it captures both the amplitude and phase information of the SHG object field.…”

High throughput second harmonic imaging for label-free biological applications

“…The second one is to parallelize the imaging process. Recent advancements [46] include wide-field counter propagating SHG geometries [10,11], lens-less imaging approaches [49], harmonic holography [50,51], multi-confocal imaging [52,53], and spatiotemporal wide-field illumination [54][55][56][57][58].…”