Edit: can alternately have a PV in photoconductive mode and it responds quicker. And if the 9 kHz is a CW tone, you can use a 567 to detect it.
You can get amplifier ICs with integral photo sensor, with a glass window. They are often in TO-5 can and sometimes in clear plastic. They can be expensive. The output is a voltage proportional to the illumination. If it's modulated light, you get an AC waveform superimposed on DC, or 50(60) Hz AC, which is the room ambient light. There is a maximum slew rate depending on what particalur device it is. the faster the slew rate, the lower the sensitivity or more expensive it is.
Or you can do your own, have a 'silicon photodiode in short-circuit mode' (look up those keywords) connected to an opamp. If you buy a PV that is very low capacitance, (and not very sensitive) you can have a fast opamp and recieve fast weak signals. If it's a higher capacitcance PV (that is sensitive), then don't waste money on fast opamps, cos these opamps won't make it much faster. To make it faster, lower the gain of the amplifier, which also reduces the sensitivity.