Note that sunlight has a smooth spectrum (some minor spiking is there, but irrelevant here).
Laser, OTOH, is extremely narrow bandwidth, and very repeatable i.e. the band does not drift.
Hence, using tight optical bandpass filters, thing about FWHM=10..20nm or so, is an easy way to decrease the sunlight contribution by maybe two orders of magnitude.
It isn't very low-cost, though; proper filters cost some serious money, they are of dichroic (interference) type. First try to deal with it electrically, which is OK with the following limitations:
* Sunlight contribution needs to be in the linear range of the sensor to be removed (if the sensor itself saturates, there is no difference if you hit it with more light, nothing AC coupling can help),
* Shot noise in the sunlight is passed through the DC removal. The more light there is, the more noise.
If you can't achieve good enough results electronically, then the next step is consider optical filtering, additionally.
In any case, we need the part number for the photodiode (or a very similar one if you can't disclose the actual part), and a schematic of your current sensing circuitry.