Why don't we use secondary lenses / optics?
LEDs typically have a plastic, silicone or glass lens over the actual LED die (the name of the chip that actually produces light); this lens helps the light produced by the LED chip escape from where it is produced. Photons produced by the silicon chip (LED die) tend to be refracted back into the chip if the surface of the die is exposed to air-- plastic and glass lenses pressed against the LED die actually help these photons to leave the LED rather than refracting back into the silicon. A primary LED Grow Light Lens is present on most LEDs to make them more efficient, and can be designed to focus light to different angles.
Secondary lenses for LEDs are designed to refocus the light from the diode and primary lens into a new, usually narrower, beam. Many grow light companies are using secondary LED optics / lenses and claim to "amplify", "magnify", or "boost the output of" the light. The secondary lenses are magnifying the light in exactly the same way a magnifying glass does in the sun- but no additional light is being produced or "harvested" from the LED, it is just being focused to a narrower beam or even a point. In fact, about 10% of the light is reflected or refracted by the secondary lens and is lost- but the remaining 90% gets focused into a more-intense beam.
If you're trying to market your product based on a single measurement of intensity, using secondary lenses will make the light really bright immediately under the center of the light so that any lumen, PAR, YPF or other intensity measurements taken there are impressive.
But just like a spotlight or laser, just off to the side of the narrow beam of light, there is almost no light. Any plants trying to grow in this region are only getting light reflected off the plants immediately under the light fixture-- but the grow light certainly looks impressive in an ad with its extremely high PAR value or "569% more light" due to "powerful optics"! Companies using secondary optics are often manipulating their PAR/PPFD readings to make their lights look much better than they really are.
Our PhytoMAX-2 LED grow lights use a primary LED lens designed to spread the light from each LED diode to maximize the even coverage of our lights over their entire intended footprint to maximize your yield. We don't want the brightest grow light as measured at a single point; our lights grow plants well over their entire footprint by spreading the light out.
Secondary lenses don't "amplify" light, they lose about 10% of it and refocus the rest to make a single measurement look better on paper, to the detriment of your plants, and that's why we don't use them.