Active Beam Steering Enabled by Photonic-Crystal Surface-Emitting Laser.

Emitting light toward on-demand directions is important for various optoelectronic applications, such as optical communication, displaying, and ranging. However, almost all existing directional emitters are assemblies of passive optical antennae and external light sources, which are usually bulky and fragile and show unendurable loss of light power. Here we theoretically propose and experimentally demonstrate a conceptual design of a directional emitter, by using a single surface-emitting laser source itself to achieve dynamically controlled beam steering. The laser is built on photonic crystals that operate near the band edges in the continuum. By shrinking laser sizes to tens-of-wavelength, the optical modes quantize in three-dimensional momentum space, and each of them directionally radiates toward the far-field. Further utilizing the luminescence spectrum shifting effect under current injection, we consecutively select a sequence of modes into lasing action and show the laser maintaining single-mode operation with line widths at a minimum of 1.8 MHz and an emitting power of ∼10 milliwatts, and we demonstrate fast beam steering across a range of 3.2° × 4° on a time scale of 500 ns. Our work proposes a method for on-chip active beam steering for the development of automotive, industrial, and robotic applications.

Acupuncture for cervical dystonia associated with anxiety and depression: A case report.

BACKGROUND: Cervical dystonia (CD) is a type of muscle tone disorder that usually occurs in the neck muscles. Due to the intermittent or continuous involuntary contraction of the neck muscles, the head and neck are twisted and skewed and some postural abnormalities occur. Long-term abnormal posture or pain can cause negative emotions in patients, which can affect their quality of life. CASE SUMMARY: This case report included a 37-year-old woman who was diagnosed with CD associated with anxiety and depression; the accompanying symptoms were head and neck tilt of approximately 90° to the right and mental abnormality. After two courses of acupuncture treatment, the patient's head and neck can be maintained in a normal position, and the negative emotions can be relieved. CONCLUSION: This case indicates that acupuncture can effectively improve CD and the emotional state and quality of life of patients, making it an effective alternative treatment for the condition.