Experimental measured for the effects of broadband pulse on the B-integral of small-scale self-focusing

It is well known that small-scale self-focusing is one of the major factors to restrict the capability and efficiency of high-power solid-state laser driver. B-integral is used to measure the severity extent of small-scale self-focusing and the typical value of B-integral is less than 1.8 in narrow band high power laser by NIF. We experimentally obtained the relationship of B-integral with spatial contrast for broadband pulse in case of active modulation and random noise modulation, and found that the growth of contrast is still very slow after B-integral up to 1.8 for 12 nm ultrashort pulse laser. So we can consider that the broadband laser is able to unloosen B-Integral criterion and then improve the system loading.