In the rapidly changing moisture air, conventional relative humidity (RH) sensors are often difficult to respond in time and accurately due to the limitation of flow rate and non-uniform airflow distribution. In this study, we numerically demonstrate that humidity changes on micro-zones can be monitored in real time using a Bloch surface wave (BSW) ubiquitous in one-dimensional photonic crystals (1DPC). This phenomenon can be observed by leakage radiation microscope (LRM). After theoretically deriving the angular resolution limit of LRM, we obtained the minimum BSW angular change on a practical scheme that can be observed in the momentum space to complete the detection, and realized the dynamic real-time monitoring of small-scale humidity change in experiment for the first time. This monitoring method has extremely high figure of merit (FOM) without hysteresis, which can be used in humidity sensing and refractive index sensing as well as the research on turbulence.

Spectral characterizations play the important roles in both scientific research and industry. Now, there is a growing demand for spectrometers that have the merits of miniaturized size, high-efficiency, and high spectral resolution. Here, a planar photonic chip containing a photonic band gap (PBG) with tailored dispersion relations is proposed to work as a high-efficient compact spectrographic device, taking advantages of its loading Bloch surface waves (BSWs). When this chip was attached to a prism, the angular dispersion power of the low-loss BSWs enhances the spectra resolving ability of this prism without any need for inversion algorithms or physical slits, thus resulting in high efficiency in utilizing the optical signals and retrieving the spectra. The spectra of various source, such as laser, white light, fluorescence emission, and even the Raman scattering light are characterized with the compact high-efficient spectrographic devices. The achieved spectral resolution can be as high as 0.6 nm.