It would be more accurate to say that Syrian, Greek, Persian and Coptic cultural achievement peaked before Islam mostly because Islam conquered those cultures and crippled them with shahada, jizyah and jihad.
Avicenna was a Persians who flourished in the Bukhara area in the first half of the eleventh century. Bukhara was militarily conquered by the Arabs in 750. They tried to rule and convert it for a hundred years without success until around 840 the Saman clan - prominent Zoroastrian nobles who converted to Islam - made it their capital.
The largely Zoroastrian population at that point began converting to Islam.
It is possible that Avicenna was only a third generation Muslim and still had Zoroastrian relatives.
Alhazen may have been Persian. He was from Basra, which was a mixed Persian and Arab city at that time. He was an almost exact contemporary of Avicenna and he was obviously very well-versed in Persian/Indian mathematics.
Clearly both were building on Persian cultural achievements - there was no Arab mathematics in the late 900s for them to draw on - but there was plenty of Persian and Indian work.
One could also mention Alfarabi, a Muslim philosopher and scientist of Baghdad in the 900s - who was tutored in the disciplines by a Monophysite Christian priest named Yochanan bin Hailan. Again, an example of a Muslim thinker who did not base his work on Islam or indigenous Arab culture.
Averroes was an Arab who lived 150 years after and 2,500 miles away from the other two. He was considered an apostate from Islam, however and his philosophical models were Greek - again there was no indigenous Arab philosophy to build on.
There was also a great period of Muslim-Jewish cooperation at the time with Maimonides in Egypt.
Of course, the only reason why Maimonides was living in Egypt instead of Cordoba is because he and his family escaped being put to the sword like the rest of the Jews of Cordoba at the hands of Sunni fanatic Abd Al-Mumin.
He prospered in Egypt under the leadership of the Kurdish non-Arab Saladin, who is acknowledged as one of medieval history's most uniquely tolerant monarchs.
Certain Arab thinkers proposed something close to heliocentric theory centuries before Copernicus did.
Bishop Nicolas Oresmes did as well.