Arduino PWM controlling high-power LED
You don't need 64kHz for this application, 200Hz is enough.

I've used the following design, for about 200mA current:

+5V --- LED --- transistor -(1)- shunt (1 Ohm) --- GND

(1) goes to the negativ input of an LM358 OpAmp. It is important that the OpAmp works down to the lower rail (GND), because there is only a small voltage on the shunt.

The output of the OpAmp drives the transistor via some appropriate resistor.

The positive input is connected to a voltage divider which is fed from the port pin. The voltage divider and the shunt determine the current through the LED.