Harshith B S, Samanta G K
Photonic Sciences Laboratory, Physical Research Laboratory, Navrangpura, Ahmedabad, Gujarat, 380009, India.
Indian Institute of Science Education and Research Pune, Dr. Homi Bhabha Road, Pashan, Pune, Maharashtra, 411008, India.
Sci Rep. 2019 Jul 29;9(1):10916. doi: 10.1038/s41598-019-47403-1.
We report on a simple and compact experimental scheme to generate high-power, ultrafast, higher-order vortex-array beams. Simply by using a dielectric microlens-array (MLA) and a plano-convex lens, we have generated array-beams carrying the spatial property of the input beam. Considering the MLA as a 2D sinusoidal phase-grating, we have numerically calculated the intensity pattern of the array-beams in close agreement with the experimental results. Using vortex beams of order as high as l = 6, we have generated vortex array-beam with individual vortices of orders up to l = 6. We have also theoretically derived the parameters controlling the intensity pattern, size, and the array-pitch and verified experimentally. The single-pass frequency-doubling of vortex-array at 1064 nm in a 1.2 mm long BiBO crystal produced green vortex-array of order, l = 12, twice the order of pump beam. Using lenses of different focal lengths, we have observed the vortex-arrays of all orders to follow a focusing dependent conversion similar to the Gaussian beam. The maximum power of the green vortex-array is measured to be 138 mW at a single-pass efficiency as high as ~3.65%. This generic experimental scheme can be used to generate the array beams of desired spatial intensity profile across a wide wavelength range by simply changing the spatial profile of the input beam.
我们报道了一种简单紧凑的实验方案，用于产生高功率、超快、高阶涡旋阵列光束。仅通过使用介电微透镜阵列（MLA）和平凸透镜，我们就生成了携带输入光束空间特性的阵列光束。将MLA视为二维正弦相位光栅，我们通过数值计算得到了阵列光束的强度分布，与实验结果高度吻合。使用高达l = 6阶的涡旋光束，我们生成了单个涡旋阶数高达l = 6的涡旋阵列光束。我们还从理论上推导了控制强度分布、尺寸和阵列间距的参数，并进行了实验验证。在1.2毫米长的BiBO晶体中，对1064纳米的涡旋阵列进行单通倍频，产生了l = 12阶的绿色涡旋阵列，其阶数是泵浦光束的两倍。使用不同焦距的透镜，我们观察到所有阶数的涡旋阵列都遵循类似于高斯光束的与聚焦相关的转换。绿色涡旋阵列的最大功率在单通效率高达约3.65%时测得为138毫瓦。这种通用的实验方案可通过简单改变输入光束的空间分布，在很宽的波长范围内生成具有所需空间强度分布的阵列光束。
