  With the LEP II Higgs search approaching exclusion limits on low values of
$\tan \beta \sim 2$ it becomes increasingly important to investigate physical
quantities sensitive to large masses of a pseudoscalar Higgs mass. This regime
is difficult and over a large range of $\tan \beta$ impossible to cover at the
LHC proton proton collider. In this paper we focus on the achievable
statistical precision of the Higgs decay into two photons at a future $\gamma
\gamma$ collider (PLC) in the MSSM mass range below 130 GeV. The MSSM and SM
predictions for $\Gamma (H \longrightarrow \gamma \gamma)$ can differ by up to
10 % even in the decoupling limit of large $m_A$. We summarize recent progress
in both the theoretical understanding of the background process $\gamma \gamma
\longrightarrow q \bar{q}$, $q=\{b,c\}$, and in the expected detector
performance allow for a high accuracy of the lightest MSSM or SM Higgs boson
decay into a $b \bar{b}$ pair. We find that for optimized but still realistic
detector and accelerator assumptions, statistically a 1.4% accuracy is feasible
after about four years of collecting data for a Higgs boson mass which excludes
$\tan \beta <2$.
